diff --git a/api/build.gradle.kts b/api/build.gradle.kts
index 8265d0532..8c7b6857c 100644
--- a/api/build.gradle.kts
+++ b/api/build.gradle.kts
@@ -16,5 +16,5 @@ dependencies {
     compileOnlyApi("org.yaml", "snakeyaml", Versions.snakeYaml)
     compileOnlyApi("io.netty", "netty-all", Versions.netty)
     compileOnlyApi("com.google.guava", "guava", Versions.guava)
-    compileOnlyApi("org.jetbrains", "annotations", Versions.jetbrainsAnnotations)
+    compileOnlyApi("org.checkerframework", "checker-qual", Versions.checkerQual)
 }
diff --git a/api/src/main/java/us/myles/ViaVersion/api/Pair.java b/api/src/main/java/us/myles/ViaVersion/api/Pair.java
index 69fa61efe..eb502791b 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/Pair.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/Pair.java
@@ -22,7 +22,7 @@
  */
 package us.myles.ViaVersion.api;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.Objects;
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/Triple.java b/api/src/main/java/us/myles/ViaVersion/api/Triple.java
index ccb43ada6..d2013bc23 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/Triple.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/Triple.java
@@ -22,7 +22,7 @@
  */
 package us.myles.ViaVersion.api;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.Objects;
 
@@ -37,18 +37,15 @@ public class Triple<A, B, C> {
         this.third = third;
     }
 
-    @Nullable
-    public A getFirst() {
+    public @Nullable A getFirst() {
         return first;
     }
 
-    @Nullable
-    public B getSecond() {
+    public @Nullable B getSecond() {
         return second;
     }
 
-    @Nullable
-    public C getThird() {
+    public @Nullable C getThird() {
         return third;
     }
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/command/ViaVersionCommand.java b/api/src/main/java/us/myles/ViaVersion/api/command/ViaVersionCommand.java
index 7961708a4..23a9c8cf2 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/command/ViaVersionCommand.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/command/ViaVersionCommand.java
@@ -22,7 +22,7 @@
  */
 package us.myles.ViaVersion.api.command;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.List;
 
@@ -49,8 +49,7 @@ public interface ViaVersionCommand {
      * @param name subcommand name
      * @return ViaSubCommand instance
      */
-    @Nullable
-    ViaSubCommand getSubCommand(String name);
+    @Nullable ViaSubCommand getSubCommand(String name);
 
     /**
      * Executed when the Command sender executes the commands
diff --git a/api/src/main/java/us/myles/ViaVersion/api/data/MappingData.java b/api/src/main/java/us/myles/ViaVersion/api/data/MappingData.java
index 1967a6a5a..2006ad5cc 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/data/MappingData.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/data/MappingData.java
@@ -23,7 +23,7 @@
 package us.myles.ViaVersion.api.data;
 
 import com.google.gson.JsonObject;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.util.Int2IntBiMap;
 
@@ -97,46 +97,38 @@ public class MappingData {
         return checkValidity(id, particleMappings.getMappings().getNewId(id), "particles");
     }
 
-    @Nullable
-    public Int2IntBiMap getItemMappings() {
+    public @Nullable Int2IntBiMap getItemMappings() {
         return itemMappings;
     }
 
-    @Nullable
-    public ParticleMappings getParticleMappings() {
+    public @Nullable ParticleMappings getParticleMappings() {
         return particleMappings;
     }
 
-    @Nullable
-    public Mappings getBlockMappings() {
+    public @Nullable Mappings getBlockMappings() {
         return blockMappings;
     }
 
-    @Nullable
-    public Mappings getBlockStateMappings() {
+    public @Nullable Mappings getBlockStateMappings() {
         return blockStateMappings;
     }
 
-    @Nullable
-    public Mappings getSoundMappings() {
+    public @Nullable Mappings getSoundMappings() {
         return soundMappings;
     }
 
-    @Nullable
-    public Mappings getStatisticsMappings() {
+    public @Nullable Mappings getStatisticsMappings() {
         return statisticsMappings;
     }
 
-    @Nullable
-    protected Mappings loadFromArray(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
+    protected @Nullable Mappings loadFromArray(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
         if (!oldMappings.has(key) || !newMappings.has(key)) return null;
 
         JsonObject diff = diffMappings != null ? diffMappings.getAsJsonObject(key) : null;
         return new Mappings(oldMappings.getAsJsonArray(key), newMappings.getAsJsonArray(key), diff);
     }
 
-    @Nullable
-    protected Mappings loadFromObject(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
+    protected @Nullable Mappings loadFromObject(JsonObject oldMappings, JsonObject newMappings, @Nullable JsonObject diffMappings, String key) {
         if (!oldMappings.has(key) || !newMappings.has(key)) return null;
 
         JsonObject diff = diffMappings != null ? diffMappings.getAsJsonObject(key) : null;
diff --git a/api/src/main/java/us/myles/ViaVersion/api/data/MappingDataLoader.java b/api/src/main/java/us/myles/ViaVersion/api/data/MappingDataLoader.java
index b09e7c484..bdfc4e3af 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/data/MappingDataLoader.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/data/MappingDataLoader.java
@@ -29,7 +29,7 @@ import com.google.gson.JsonObject;
 import com.google.gson.JsonSyntaxException;
 import it.unimi.dsi.fastutil.objects.Object2IntMap;
 import it.unimi.dsi.fastutil.objects.Object2IntOpenHashMap;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.util.GsonUtil;
 import us.myles.ViaVersion.util.Int2IntBiMap;
@@ -73,8 +73,7 @@ public class MappingDataLoader {
     /**
      * Loads the file from the plugin folder if present, else from the bundled resources.
      */
-    @Nullable
-    public static JsonObject loadFromDataDir(String name) {
+    public static @Nullable JsonObject loadFromDataDir(String name) {
         File file = new File(Via.getPlatform().getDataFolder(), name);
         if (!file.exists()) return loadData(name);
 
@@ -94,8 +93,7 @@ public class MappingDataLoader {
     /**
      * Loads the file from the bundled resources. Uses the cache if enabled.
      */
-    @Nullable
-    public static JsonObject loadData(String name) {
+    public static @Nullable JsonObject loadData(String name) {
         return loadData(name, false);
     }
 
@@ -104,8 +102,7 @@ public class MappingDataLoader {
      *
      * @param cacheIfEnabled whether loaded files should be cached
      */
-    @Nullable
-    public static JsonObject loadData(String name, boolean cacheIfEnabled) {
+    public static @Nullable JsonObject loadData(String name, boolean cacheIfEnabled) {
         if (cacheJsonMappings) {
             JsonObject cached = MAPPINGS_CACHE.get(name);
             if (cached != null) {
@@ -233,8 +230,7 @@ public class MappingDataLoader {
         return map;
     }
 
-    @Nullable
-    public static InputStream getResource(String name) {
+    public static @Nullable InputStream getResource(String name) {
         return MappingDataLoader.class.getClassLoader().getResourceAsStream("assets/viaversion/data/" + name);
     }
 }
diff --git a/api/src/main/java/us/myles/ViaVersion/api/data/Mappings.java b/api/src/main/java/us/myles/ViaVersion/api/data/Mappings.java
index fb798502d..fbe402d1c 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/data/Mappings.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/data/Mappings.java
@@ -24,7 +24,7 @@ package us.myles.ViaVersion.api.data;
 
 import com.google.gson.JsonArray;
 import com.google.gson.JsonObject;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.Arrays;
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/data/UserConnection.java b/api/src/main/java/us/myles/ViaVersion/api/data/UserConnection.java
index b3c1adee7..8606850ea 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/data/UserConnection.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/data/UserConnection.java
@@ -27,7 +27,7 @@ import io.netty.buffer.ByteBuf;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelHandlerContext;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.PacketWrapper;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.ViaVersionConfig;
@@ -96,8 +96,7 @@ public class UserConnection {
      * @param <T>         The type of the class you want to get.
      * @return The requested object
      */
-    @Nullable
-    public <T extends StoredObject> T get(Class<T> objectClass) {
+    public @Nullable <T extends StoredObject> T get(Class<T> objectClass) {
         return (T) storedObjects.get(objectClass);
     }
 
@@ -453,13 +452,11 @@ public class UserConnection {
         return id;
     }
 
-    @Nullable
-    public Channel getChannel() {
+    public @Nullable Channel getChannel() {
         return channel;
     }
 
-    @Nullable
-    public ProtocolInfo getProtocolInfo() {
+    public @Nullable ProtocolInfo getProtocolInfo() {
         return protocolInfo;
     }
 
@@ -492,8 +489,7 @@ public class UserConnection {
         this.pendingDisconnect = pendingDisconnect;
     }
 
-    @Nullable
-    public Object getLastPacket() {
+    public @Nullable Object getLastPacket() {
         return lastPacket;
     }
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/entities/EntityType.java b/api/src/main/java/us/myles/ViaVersion/api/entities/EntityType.java
index 248cbe68c..17c77c4e2 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/entities/EntityType.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/entities/EntityType.java
@@ -22,7 +22,7 @@
  */
 package us.myles.ViaVersion.api.entities;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public interface EntityType {
 
@@ -34,16 +34,16 @@ public interface EntityType {
     /**
      * @return parent entity type if present
      */
-    @Nullable
-    EntityType getParent();
+    @Nullable EntityType getParent();
 
     String name();
 
     default boolean is(EntityType... types) {
-        for (EntityType type : types)
+        for (EntityType type : types) {
             if (this == type) {
                 return true;
             }
+        }
         return false;
     }
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/BaseChunk.java b/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/BaseChunk.java
index 85d410e13..5663f1a8b 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/BaseChunk.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/BaseChunk.java
@@ -23,7 +23,7 @@
 package us.myles.ViaVersion.api.minecraft.chunks;
 
 import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.BitSet;
 import java.util.List;
@@ -42,7 +42,7 @@ public class BaseChunk implements Chunk {
     protected final List<CompoundTag> blockEntities;
 
     public BaseChunk(int x, int z, boolean fullChunk, boolean ignoreOldLightData, @Nullable BitSet chunkSectionBitSet,
-                     ChunkSection[] sections, @Nullable int[] biomeData, @Nullable CompoundTag heightMap, List<CompoundTag> blockEntities) {
+                     ChunkSection[] sections, int @Nullable [] biomeData, @Nullable CompoundTag heightMap, List<CompoundTag> blockEntities) {
         this.x = x;
         this.z = z;
         this.fullChunk = fullChunk;
@@ -104,8 +104,7 @@ public class BaseChunk implements Chunk {
     }
 
     @Override
-    @Nullable
-    public BitSet getChunkMask() {
+    public @Nullable BitSet getChunkMask() {
         return chunkSectionBitSet;
     }
 
@@ -125,13 +124,12 @@ public class BaseChunk implements Chunk {
     }
 
     @Override
-    @Nullable
-    public int[] getBiomeData() {
+    public int @Nullable [] getBiomeData() {
         return biomeData;
     }
 
     @Override
-    public void setBiomeData(final int[] biomeData) {
+    public void setBiomeData(int @Nullable [] biomeData) {
         this.biomeData = biomeData;
     }
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/Chunk.java b/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/Chunk.java
index 14cec0f35..dd9a55d20 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/Chunk.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/Chunk.java
@@ -23,7 +23,7 @@
 package us.myles.ViaVersion.api.minecraft.chunks;
 
 import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.BitSet;
 import java.util.List;
@@ -65,8 +65,7 @@ public interface Chunk {
      * @return chunk section bit mask, only non-null available for 1.17+ chunks
      * @see #getBitmask()
      */
-    @Nullable
-    BitSet getChunkMask();
+    @Nullable BitSet getChunkMask();
 
     void setChunkMask(BitSet chunkSectionMask);
 
@@ -74,10 +73,9 @@ public interface Chunk {
 
     void setSections(ChunkSection[] sections);
 
-    @Nullable
-    int[] getBiomeData();
+    int @Nullable [] getBiomeData();
 
-    void setBiomeData(int[] biomeData);
+    void setBiomeData(int @Nullable [] biomeData);
 
     CompoundTag getHeightMap();
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/ChunkSection.java b/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/ChunkSection.java
index d3f55d818..10c697fb2 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/ChunkSection.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/minecraft/chunks/ChunkSection.java
@@ -27,7 +27,7 @@ import it.unimi.dsi.fastutil.ints.Int2IntMap;
 import it.unimi.dsi.fastutil.ints.Int2IntOpenHashMap;
 import it.unimi.dsi.fastutil.ints.IntArrayList;
 import it.unimi.dsi.fastutil.ints.IntList;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class ChunkSection {
 
@@ -207,23 +207,19 @@ public class ChunkSection {
         }
     }
 
-    @Nullable
-    public byte[] getBlockLight() {
+    public @Nullable byte[] getBlockLight() {
         return blockLight == null ? null : blockLight.getHandle();
     }
 
-    @Nullable
-    public NibbleArray getBlockLightNibbleArray() {
+    public @Nullable NibbleArray getBlockLightNibbleArray() {
         return blockLight;
     }
 
-    @Nullable
-    public byte[] getSkyLight() {
+    public @Nullable byte[] getSkyLight() {
         return skyLight == null ? null : skyLight.getHandle();
     }
 
-    @Nullable
-    public NibbleArray getSkyLightNibbleArray() {
+    public @Nullable NibbleArray getSkyLightNibbleArray() {
         return skyLight;
     }
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/minecraft/item/Item.java b/api/src/main/java/us/myles/ViaVersion/api/minecraft/item/Item.java
index c21b2ab43..be2c5ca5a 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/minecraft/item/Item.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/minecraft/item/Item.java
@@ -24,7 +24,7 @@ package us.myles.ViaVersion.api.minecraft.item;
 
 import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
 import com.google.gson.annotations.SerializedName;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.Objects;
 
@@ -73,8 +73,7 @@ public class Item {
         this.data = data;
     }
 
-    @Nullable
-    public CompoundTag getTag() {
+    public @Nullable CompoundTag getTag() {
         return tag;
     }
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/minecraft/nbt/BinaryTagIO.java b/api/src/main/java/us/myles/ViaVersion/api/minecraft/nbt/BinaryTagIO.java
index 129ae556b..53652353a 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/minecraft/nbt/BinaryTagIO.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/minecraft/nbt/BinaryTagIO.java
@@ -24,7 +24,7 @@
 package us.myles.ViaVersion.api.minecraft.nbt;
 
 import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
-import org.jetbrains.annotations.NotNull;
+import org.checkerframework.checker.nullness.qual.NonNull;
 
 import java.io.BufferedInputStream;
 import java.io.DataInput;
@@ -53,8 +53,7 @@ public final class BinaryTagIO {
      * @return the compound tag
      * @throws IOException if an exception was encountered while reading a compound tag
      */
-    @NotNull
-    public static CompoundTag readPath(final @NotNull Path path) throws IOException {
+    public static @NonNull CompoundTag readPath(final @NonNull Path path) throws IOException {
         return readInputStream(Files.newInputStream(path));
     }
 
@@ -65,8 +64,7 @@ public final class BinaryTagIO {
      * @return the compound tag
      * @throws IOException if an exception was encountered while reading a compound tag
      */
-    @NotNull
-    public static CompoundTag readInputStream(final @NotNull InputStream input) throws IOException {
+    public static @NonNull CompoundTag readInputStream(final @NonNull InputStream input) throws IOException {
         try (final DataInputStream dis = new DataInputStream(input)) {
             return readDataInput(dis);
         }
@@ -79,8 +77,7 @@ public final class BinaryTagIO {
      * @return the compound tag
      * @throws IOException if an exception was encountered while reading a compound tag
      */
-    @NotNull
-    public static CompoundTag readCompressedPath(final @NotNull Path path) throws IOException {
+    public static @NonNull CompoundTag readCompressedPath(final @NonNull Path path) throws IOException {
         return readCompressedInputStream(Files.newInputStream(path));
     }
 
@@ -91,8 +88,7 @@ public final class BinaryTagIO {
      * @return the compound tag
      * @throws IOException if an exception was encountered while reading a compound tag
      */
-    @NotNull
-    public static CompoundTag readCompressedInputStream(final @NotNull InputStream input) throws IOException {
+    public static @NonNull CompoundTag readCompressedInputStream(final @NonNull InputStream input) throws IOException {
         try (final DataInputStream dis = new DataInputStream(new BufferedInputStream(new GZIPInputStream(input)))) {
             return readDataInput(dis);
         }
@@ -105,8 +101,7 @@ public final class BinaryTagIO {
      * @return the compound tag
      * @throws IOException if an exception was encountered while reading a compound tag
      */
-    @NotNull
-    public static CompoundTag readDataInput(final @NotNull DataInput input) throws IOException {
+    public static @NonNull CompoundTag readDataInput(final @NonNull DataInput input) throws IOException {
         byte type = input.readByte();
         if (type != CompoundTag.ID) {
             throw new IOException(String.format("Expected root tag to be a CompoundTag, was %s", type));
@@ -125,7 +120,7 @@ public final class BinaryTagIO {
      * @param path the path
      * @throws IOException if an exception was encountered while writing the compound tag
      */
-    public static void writePath(final @NotNull CompoundTag tag, final @NotNull Path path) throws IOException {
+    public static void writePath(final @NonNull CompoundTag tag, final @NonNull Path path) throws IOException {
         writeOutputStream(tag, Files.newOutputStream(path));
     }
 
@@ -136,7 +131,7 @@ public final class BinaryTagIO {
      * @param output the output stream
      * @throws IOException if an exception was encountered while writing the compound tag
      */
-    public static void writeOutputStream(final @NotNull CompoundTag tag, final @NotNull OutputStream output) throws IOException {
+    public static void writeOutputStream(final @NonNull CompoundTag tag, final @NonNull OutputStream output) throws IOException {
         try (final DataOutputStream dos = new DataOutputStream(output)) {
             writeDataOutput(tag, dos);
         }
@@ -149,7 +144,7 @@ public final class BinaryTagIO {
      * @param path the path
      * @throws IOException if an exception was encountered while writing the compound tag
      */
-    public static void writeCompressedPath(final @NotNull CompoundTag tag, final @NotNull Path path) throws IOException {
+    public static void writeCompressedPath(final @NonNull CompoundTag tag, final @NonNull Path path) throws IOException {
         writeCompressedOutputStream(tag, Files.newOutputStream(path));
     }
 
@@ -160,7 +155,7 @@ public final class BinaryTagIO {
      * @param output the output stream
      * @throws IOException if an exception was encountered while writing the compound tag
      */
-    public static void writeCompressedOutputStream(final @NotNull CompoundTag tag, final @NotNull OutputStream output) throws IOException {
+    public static void writeCompressedOutputStream(final @NonNull CompoundTag tag, final @NonNull OutputStream output) throws IOException {
         try (final DataOutputStream dos = new DataOutputStream(new GZIPOutputStream(output))) {
             writeDataOutput(tag, dos);
         }
@@ -173,7 +168,7 @@ public final class BinaryTagIO {
      * @param output the output
      * @throws IOException if an exception was encountered while writing the compound tag
      */
-    public static void writeDataOutput(final @NotNull CompoundTag tag, final @NotNull DataOutput output) throws IOException {
+    public static void writeDataOutput(final @NonNull CompoundTag tag, final @NonNull DataOutput output) throws IOException {
         output.writeByte(CompoundTag.ID);
         output.writeUTF(""); // write empty name
         tag.write(output);
@@ -186,8 +181,7 @@ public final class BinaryTagIO {
      * @return the compound tag
      * @throws IOException if an exception was encountered while reading a compound tag
      */
-    @NotNull
-    public static CompoundTag readString(final @NotNull String input) throws IOException {
+    public static @NonNull CompoundTag readString(final @NonNull String input) throws IOException {
         try {
             final CharBuffer buffer = new CharBuffer(input);
             final TagStringReader parser = new TagStringReader(buffer);
@@ -208,8 +202,7 @@ public final class BinaryTagIO {
      * @return the string
      * @throws IOException if an exception was encountered while writing the compound tag
      */
-    @NotNull
-    public static String writeString(final @NotNull CompoundTag tag) throws IOException {
+    public static @NonNull String writeString(final @NonNull CompoundTag tag) throws IOException {
         final StringBuilder sb = new StringBuilder();
         try (final TagStringWriter emit = new TagStringWriter(sb)) {
             emit.writeTag(tag);
diff --git a/api/src/main/java/us/myles/ViaVersion/api/platform/ViaConnectionManager.java b/api/src/main/java/us/myles/ViaVersion/api/platform/ViaConnectionManager.java
index d36f6004e..2712493f0 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/platform/ViaConnectionManager.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/platform/ViaConnectionManager.java
@@ -23,11 +23,15 @@
 package us.myles.ViaVersion.api.platform;
 
 import io.netty.channel.ChannelFutureListener;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.UserConnection;
 
-import java.util.*;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 
 /**
@@ -44,7 +48,7 @@ public class ViaConnectionManager {
         if (isFrontEnd(connection)) {
             UUID id = connection.getProtocolInfo().getUuid();
             if (clients.put(id, connection) != null) {
-                Via.getPlatform().getLogger().warning("Duplicate UUID on frontend connection! ("+id+")");
+                Via.getPlatform().getLogger().warning("Duplicate UUID on frontend connection! (" + id + ")");
             }
         }
 
@@ -90,8 +94,7 @@ public class ViaConnectionManager {
      * Note that connections are removed as soon as their channel is closed,
      * so avoid using this method during player quits for example.
      */
-    @Nullable
-    public UserConnection getConnectedClient(UUID clientIdentifier) {
+    public @Nullable UserConnection getConnectedClient(UUID clientIdentifier) {
         return clients.get(clientIdentifier);
     }
 
@@ -104,8 +107,7 @@ public class ViaConnectionManager {
      * Note that connections are removed as soon as their channel is closed,
      * so avoid using this method during player quits for example.
      */
-    @Nullable
-    public UUID getConnectedClientId(UserConnection conn) {
+    public @Nullable UUID getConnectedClientId(UserConnection conn) {
         if (conn.getProtocolInfo() == null) return null;
         UUID uuid = conn.getProtocolInfo().getUuid();
         UserConnection client = clients.get(uuid);
diff --git a/api/src/main/java/us/myles/ViaVersion/api/platform/providers/ViaProviders.java b/api/src/main/java/us/myles/ViaVersion/api/platform/providers/ViaProviders.java
index 8407425bb..42d5738dc 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/platform/providers/ViaProviders.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/platform/providers/ViaProviders.java
@@ -22,7 +22,7 @@
  */
 package us.myles.ViaVersion.api.platform.providers;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -46,8 +46,7 @@ public class ViaProviders {
         providers.put(provider, value);
     }
 
-    @Nullable
-    public <T extends Provider> T get(Class<T> provider) {
+    public @Nullable <T extends Provider> T get(Class<T> provider) {
         Provider rawProvider = providers.get(provider);
         if (rawProvider != null) {
             return (T) rawProvider;
diff --git a/api/src/main/java/us/myles/ViaVersion/api/protocol/Protocol.java b/api/src/main/java/us/myles/ViaVersion/api/protocol/Protocol.java
index 77f69a8c9..31b9ec7c9 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/protocol/Protocol.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/protocol/Protocol.java
@@ -23,7 +23,7 @@
 package us.myles.ViaVersion.api.protocol;
 
 import com.google.common.base.Preconditions;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.PacketWrapper;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.MappingData;
@@ -472,8 +472,7 @@ public abstract class Protocol<C1 extends ClientboundPacketType, C2 extends Clie
         }
     }
 
-    @Nullable
-    public <T> T get(Class<T> objectClass) {
+    public @Nullable <T> T get(Class<T> objectClass) {
         return (T) storedObjects.get(objectClass);
     }
 
@@ -493,8 +492,7 @@ public abstract class Protocol<C1 extends ClientboundPacketType, C2 extends Clie
         return getMappingData() != null;
     }
 
-    @Nullable
-    public MappingData getMappingData() {
+    public @Nullable MappingData getMappingData() {
         return null; // Let the protocols hold the mappings to still have easy, static singleton access there
     }
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolManager.java b/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolManager.java
index 3076eb33d..9ebc748f8 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolManager.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolManager.java
@@ -23,7 +23,7 @@
 package us.myles.ViaVersion.api.protocol;
 
 import com.google.common.collect.Range;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.List;
 import java.util.SortedSet;
@@ -44,8 +44,7 @@ public interface ProtocolManager {
      * @param protocolClass class of the protocol
      * @return protocol if present
      */
-    @Nullable
-    Protocol getProtocol(Class<? extends Protocol> protocolClass);
+    @Nullable Protocol getProtocol(Class<? extends Protocol> protocolClass);
 
     Protocol getBaseProtocol();
 
@@ -87,8 +86,7 @@ public interface ProtocolManager {
      * @param serverVersion desired output server version
      * @return path it generated, null if not supported
      */
-    @Nullable
-    List<ProtocolPathEntry> getProtocolPath(int clientVersion, int serverVersion);
+    @Nullable List<ProtocolPathEntry> getProtocolPath(int clientVersion, int serverVersion);
 
     /**
      * Returns the maximum protocol path size applied to {@link #getProtocolPath(int, int)}.
@@ -159,6 +157,5 @@ public interface ProtocolManager {
      * @param protocolClass protocol class
      * @return data loading future bound to the protocol, or null if all loading is complete
      */
-    @Nullable
-    CompletableFuture<Void> getMappingLoaderFuture(Class<? extends Protocol> protocolClass);
+    @Nullable CompletableFuture<Void> getMappingLoaderFuture(Class<? extends Protocol> protocolClass);
 }
diff --git a/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolRegistry.java b/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolRegistry.java
index b4dc3e5ad..3e73ed185 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolRegistry.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolRegistry.java
@@ -23,7 +23,7 @@
 package us.myles.ViaVersion.api.protocol;
 
 import com.google.common.collect.Range;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.ViaManager;
 import us.myles.ViaVersion.api.Pair;
 import us.myles.ViaVersion.api.Via;
@@ -103,8 +103,7 @@ public class ProtocolRegistry {
      * @param serverVersion The desired output server version
      * @return The path it generated, null if it failed.
      */
-    @Nullable
-    public static List<Pair<Integer, Protocol>> getProtocolPath(int clientVersion, int serverVersion) {
+    public static @Nullable List<Pair<Integer, Protocol>> getProtocolPath(int clientVersion, int serverVersion) {
         List<ProtocolPathEntry> pathList = Via.getManager().getProtocolManager().getProtocolPath(clientVersion, serverVersion);
         if (pathList == null) {
             return null;
@@ -123,8 +122,7 @@ public class ProtocolRegistry {
      * @param protocolClass class of the protocol
      * @return protocol if present
      */
-    @Nullable
-    public static Protocol getProtocol(Class<? extends Protocol> protocolClass) {
+    public static @Nullable Protocol getProtocol(Class<? extends Protocol> protocolClass) {
         return Via.getManager().getProtocolManager().getProtocol(protocolClass);
     }
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolVersion.java b/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolVersion.java
index 759419223..ce2aafd97 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolVersion.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolVersion.java
@@ -25,8 +25,8 @@ package us.myles.ViaVersion.api.protocol;
 import com.google.common.base.Preconditions;
 import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -105,8 +105,7 @@ public class ProtocolVersion {
         return versions.containsKey(id);
     }
 
-    @NotNull
-    public static ProtocolVersion getProtocol(int id) {
+    public static @NonNull ProtocolVersion getProtocol(int id) {
         ProtocolVersion protocolVersion = versions.get(id);
         if (protocolVersion != null) {
             return protocolVersion;
@@ -123,8 +122,7 @@ public class ProtocolVersion {
         return Collections.unmodifiableList(new ArrayList<>(versions.values()));
     }
 
-    @Nullable
-    public static ProtocolVersion getClosest(String protocol) {
+    public static @Nullable ProtocolVersion getClosest(String protocol) {
         for (ProtocolVersion version : versions.values()) {
             String name = version.getName();
             if (name.equals(protocol)) {
@@ -211,6 +209,10 @@ public class ProtocolVersion {
         return snapshotVersion == -1 ? version : ((1 << 30) | snapshotVersion);
     }
 
+    public boolean isKnown() {
+        return version != -1;
+    }
+
     /**
      * @return true if the protocol includes a range of versions (but not an entire major version range), for example 1.7-1.7.5
      * @see #getIncludedVersions()
diff --git a/api/src/main/java/us/myles/ViaVersion/api/protocol/ServerProtocolVersion.java b/api/src/main/java/us/myles/ViaVersion/api/protocol/ServerProtocolVersion.java
index 3026ea80b..654916d18 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/protocol/ServerProtocolVersion.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/protocol/ServerProtocolVersion.java
@@ -49,7 +49,7 @@ public interface ServerProtocolVersion {
      * Returns true if the actual protocol version has not yet been identified.
      * In that case, all methods above will returns -1.
      *
-     * @return true if unset
+     * @return true if set, false if unknown (yet)
      */
     default boolean isKnown() {
         return lowestSupportedVersion() != -1 && highestSupportedVersion() != -1;
diff --git a/api/src/main/java/us/myles/ViaVersion/api/remapper/ValueTransformer.java b/api/src/main/java/us/myles/ViaVersion/api/remapper/ValueTransformer.java
index 6eb59edfb..4089c57ed 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/remapper/ValueTransformer.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/remapper/ValueTransformer.java
@@ -22,7 +22,7 @@
  */
 package us.myles.ViaVersion.api.remapper;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.PacketWrapper;
 import us.myles.ViaVersion.api.type.Type;
 import us.myles.ViaVersion.exception.InformativeException;
@@ -60,8 +60,7 @@ public abstract class ValueTransformer<T1, T2> implements ValueWriter<T1> {
         }
     }
 
-    @Nullable
-    public Type<T1> getInputType() {
+    public @Nullable Type<T1> getInputType() {
         return inputType;
     }
 
diff --git a/api/src/main/java/us/myles/ViaVersion/api/type/Type.java b/api/src/main/java/us/myles/ViaVersion/api/type/Type.java
index 96c4e0dcf..24e51235b 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/type/Type.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/type/Type.java
@@ -31,7 +31,28 @@ import us.myles.ViaVersion.api.minecraft.Position;
 import us.myles.ViaVersion.api.minecraft.Vector;
 import us.myles.ViaVersion.api.minecraft.VillagerData;
 import us.myles.ViaVersion.api.minecraft.item.Item;
-import us.myles.ViaVersion.api.type.types.*;
+import us.myles.ViaVersion.api.type.types.ArrayType;
+import us.myles.ViaVersion.api.type.types.BooleanType;
+import us.myles.ViaVersion.api.type.types.ByteArrayType;
+import us.myles.ViaVersion.api.type.types.ByteType;
+import us.myles.ViaVersion.api.type.types.ComponentType;
+import us.myles.ViaVersion.api.type.types.DoubleType;
+import us.myles.ViaVersion.api.type.types.FloatType;
+import us.myles.ViaVersion.api.type.types.IntType;
+import us.myles.ViaVersion.api.type.types.LongArrayType;
+import us.myles.ViaVersion.api.type.types.LongType;
+import us.myles.ViaVersion.api.type.types.RemainingBytesType;
+import us.myles.ViaVersion.api.type.types.ShortByteArrayType;
+import us.myles.ViaVersion.api.type.types.ShortType;
+import us.myles.ViaVersion.api.type.types.StringType;
+import us.myles.ViaVersion.api.type.types.UUIDIntArrayType;
+import us.myles.ViaVersion.api.type.types.UUIDType;
+import us.myles.ViaVersion.api.type.types.UnsignedByteType;
+import us.myles.ViaVersion.api.type.types.UnsignedShortType;
+import us.myles.ViaVersion.api.type.types.VarIntArrayType;
+import us.myles.ViaVersion.api.type.types.VarIntType;
+import us.myles.ViaVersion.api.type.types.VarLongType;
+import us.myles.ViaVersion.api.type.types.VoidType;
 import us.myles.ViaVersion.api.type.types.minecraft.BlockChangeRecordType;
 import us.myles.ViaVersion.api.type.types.minecraft.EulerAngleType;
 import us.myles.ViaVersion.api.type.types.minecraft.FlatItemArrayType;
diff --git a/api/src/main/java/us/myles/ViaVersion/api/type/types/StringType.java b/api/src/main/java/us/myles/ViaVersion/api/type/types/StringType.java
index 12df774ef..bde85d522 100644
--- a/api/src/main/java/us/myles/ViaVersion/api/type/types/StringType.java
+++ b/api/src/main/java/us/myles/ViaVersion/api/type/types/StringType.java
@@ -48,7 +48,7 @@ public class StringType extends Type<String> {
         int len = Type.VAR_INT.readPrimitive(buffer);
 
         Preconditions.checkArgument(len <= maxLength * maxJavaCharUtf8Length,
-                "Cannot receive string longer than Short.MAX_VALUE * "  + maxJavaCharUtf8Length + " bytes (got %s bytes)", len);
+                "Cannot receive string longer than Short.MAX_VALUE * " + maxJavaCharUtf8Length + " bytes (got %s bytes)", len);
 
         String string = buffer.toString(buffer.readerIndex(), len, StandardCharsets.UTF_8);
         buffer.skipBytes(len);
diff --git a/api/src/main/java/us/myles/ViaVersion/util/CompactArrayUtil.java b/api/src/main/java/us/myles/ViaVersion/util/CompactArrayUtil.java
index aaf542ef3..5dbc2ab20 100644
--- a/api/src/main/java/us/myles/ViaVersion/util/CompactArrayUtil.java
+++ b/api/src/main/java/us/myles/ViaVersion/util/CompactArrayUtil.java
@@ -46,7 +46,7 @@ public class CompactArrayUtil {
             79536431, 0, 78090314, 78090314, 0, 76695844, 76695844, 0, 75350303, 75350303,
             0, 74051160, 74051160, 0, 72796055, 72796055, 0, 71582788, 71582788, 0,
             70409299, 70409299, 0, 69273666, 69273666, 0, 68174084, 68174084, 0, Integer.MIN_VALUE,
-            0, 5 };
+            0, 5};
 
     private CompactArrayUtil() {
         throw new AssertionError();
@@ -72,6 +72,7 @@ public class CompactArrayUtil {
 
         return data;
     }
+
     public static void iterateCompactArrayWithPadding(int bitsPerEntry, int entries, long[] data, BiIntConsumer consumer) {
         long maxEntryValue = (1L << bitsPerEntry) - 1;
         char valuesPerLong = (char) (64 / bitsPerEntry);
diff --git a/api/src/main/java/us/myles/ViaVersion/util/Int2IntBiMap.java b/api/src/main/java/us/myles/ViaVersion/util/Int2IntBiMap.java
index 61fdb0834..1432525f6 100644
--- a/api/src/main/java/us/myles/ViaVersion/util/Int2IntBiMap.java
+++ b/api/src/main/java/us/myles/ViaVersion/util/Int2IntBiMap.java
@@ -27,7 +27,7 @@ import it.unimi.dsi.fastutil.ints.Int2IntMap;
 import it.unimi.dsi.fastutil.ints.Int2IntOpenHashMap;
 import it.unimi.dsi.fastutil.ints.IntSet;
 import it.unimi.dsi.fastutil.objects.ObjectSet;
-import org.jetbrains.annotations.NotNull;
+import org.checkerframework.checker.nullness.qual.NonNull;
 
 import java.util.Map;
 
@@ -106,7 +106,7 @@ public class Int2IntBiMap implements Int2IntMap {
 
     @Override
     @Deprecated
-    public void putAll(@NotNull Map<? extends Integer, ? extends Integer> m) {
+    public void putAll(@NonNull Map<? extends Integer, ? extends Integer> m) {
         throw new UnsupportedOperationException();
     }
 
@@ -127,14 +127,12 @@ public class Int2IntBiMap implements Int2IntMap {
     }
 
     @Override
-    @NotNull
-    public IntSet keySet() {
+    public @NonNull IntSet keySet() {
         return map.keySet();
     }
 
     @Override
-    @NotNull
-    public IntSet values() {
+    public @NonNull IntSet values() {
         return inverse.map.keySet();
     }
 
diff --git a/buildSrc/src/main/kotlin/Versions.kt b/buildSrc/src/main/kotlin/Versions.kt
index 1a0a2d648..b8a26c6a5 100644
--- a/buildSrc/src/main/kotlin/Versions.kt
+++ b/buildSrc/src/main/kotlin/Versions.kt
@@ -11,8 +11,8 @@ object Versions {
     const val guava = "17.0"
     const val snakeYaml = "1.18"
 
-    const val jetbrainsAnnotations = "20.1.0"
     const val jUnit = "5.6.3"
+    const val checkerQual = "3.12.0"
 
     // Platforms
     const val spigot = "1.16.5-R0.1-SNAPSHOT"
diff --git a/bukkit/src/main/java/us/myles/ViaVersion/bukkit/handlers/BukkitEncodeHandler.java b/bukkit/src/main/java/us/myles/ViaVersion/bukkit/handlers/BukkitEncodeHandler.java
index cee0aa6dc..c840055f2 100644
--- a/bukkit/src/main/java/us/myles/ViaVersion/bukkit/handlers/BukkitEncodeHandler.java
+++ b/bukkit/src/main/java/us/myles/ViaVersion/bukkit/handlers/BukkitEncodeHandler.java
@@ -71,7 +71,7 @@ public class BukkitEncodeHandler extends MessageToByteEncoder implements ViaHand
                     throw (Error) e.getCause();
                 }
             }
-            
+
         } else {
             bytebuf.writeBytes((ByteBuf) o);
         }
diff --git a/bukkit/src/main/java/us/myles/ViaVersion/bukkit/listeners/multiversion/PlayerSneakListener.java b/bukkit/src/main/java/us/myles/ViaVersion/bukkit/listeners/multiversion/PlayerSneakListener.java
index e97a86fa3..b63fc5dcd 100644
--- a/bukkit/src/main/java/us/myles/ViaVersion/bukkit/listeners/multiversion/PlayerSneakListener.java
+++ b/bukkit/src/main/java/us/myles/ViaVersion/bukkit/listeners/multiversion/PlayerSneakListener.java
@@ -32,7 +32,11 @@ import us.myles.ViaVersion.protocols.base.ProtocolInfo;
 
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
-import java.util.*;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+import java.util.WeakHashMap;
 
 public class PlayerSneakListener extends ViaBukkitListener {
     private static final float STANDING_HEIGHT = 1.8F;
diff --git a/bungee/src/main/java/us/myles/ViaVersion/BungeePlugin.java b/bungee/src/main/java/us/myles/ViaVersion/BungeePlugin.java
index a169ae132..74db72ea3 100644
--- a/bungee/src/main/java/us/myles/ViaVersion/BungeePlugin.java
+++ b/bungee/src/main/java/us/myles/ViaVersion/BungeePlugin.java
@@ -43,8 +43,8 @@ import us.myles.ViaVersion.dump.PluginInfo;
 import us.myles.ViaVersion.util.GsonUtil;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.UUID;
 import java.util.concurrent.TimeUnit;
diff --git a/bungee/src/main/java/us/myles/ViaVersion/bungee/handlers/BungeeDecodeHandler.java b/bungee/src/main/java/us/myles/ViaVersion/bungee/handlers/BungeeDecodeHandler.java
index ae6afb9c8..62003d98d 100644
--- a/bungee/src/main/java/us/myles/ViaVersion/bungee/handlers/BungeeDecodeHandler.java
+++ b/bungee/src/main/java/us/myles/ViaVersion/bungee/handlers/BungeeDecodeHandler.java
@@ -22,8 +22,8 @@ import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.MessageToMessageDecoder;
 import us.myles.ViaVersion.api.data.UserConnection;
-import us.myles.ViaVersion.exception.CancelDecoderException;
 import us.myles.ViaVersion.exception.CancelCodecException;
+import us.myles.ViaVersion.exception.CancelDecoderException;
 
 import java.util.List;
 
diff --git a/bungee/src/main/java/us/myles/ViaVersion/bungee/handlers/BungeeEncodeHandler.java b/bungee/src/main/java/us/myles/ViaVersion/bungee/handlers/BungeeEncodeHandler.java
index f72d6301d..020cb2d85 100644
--- a/bungee/src/main/java/us/myles/ViaVersion/bungee/handlers/BungeeEncodeHandler.java
+++ b/bungee/src/main/java/us/myles/ViaVersion/bungee/handlers/BungeeEncodeHandler.java
@@ -23,8 +23,8 @@ import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.MessageToMessageEncoder;
 import us.myles.ViaVersion.api.data.UserConnection;
 import us.myles.ViaVersion.bungee.util.BungeePipelineUtil;
-import us.myles.ViaVersion.exception.CancelEncoderException;
 import us.myles.ViaVersion.exception.CancelCodecException;
+import us.myles.ViaVersion.exception.CancelEncoderException;
 
 import java.util.List;
 
diff --git a/bungee/src/main/java/us/myles/ViaVersion/bungee/platform/BungeeViaConfig.java b/bungee/src/main/java/us/myles/ViaVersion/bungee/platform/BungeeViaConfig.java
index 8ac8e46ae..2e3e8d46e 100644
--- a/bungee/src/main/java/us/myles/ViaVersion/bungee/platform/BungeeViaConfig.java
+++ b/bungee/src/main/java/us/myles/ViaVersion/bungee/platform/BungeeViaConfig.java
@@ -23,7 +23,11 @@ import us.myles.ViaVersion.bungee.providers.BungeeVersionProvider;
 
 import java.io.File;
 import java.net.URL;
-import java.util.*;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
 
 public class BungeeViaConfig extends AbstractViaConfig {
     private static final List<String> UNSUPPORTED = Arrays.asList("nms-player-ticking", "item-cache", "anti-xray-patch", "quick-move-action-fix", "velocity-ping-interval", "velocity-ping-save", "velocity-servers", "blockconnection-method", "change-1_9-hitbox", "change-1_14-hitbox");
diff --git a/common/src/main/java/us/myles/ViaVersion/api/ViaListener.java b/common/src/main/java/us/myles/ViaVersion/api/ViaListener.java
index 713d4b6b2..2772903e3 100644
--- a/common/src/main/java/us/myles/ViaVersion/api/ViaListener.java
+++ b/common/src/main/java/us/myles/ViaVersion/api/ViaListener.java
@@ -17,7 +17,7 @@
  */
 package us.myles.ViaVersion.api;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.data.UserConnection;
 import us.myles.ViaVersion.api.protocol.Protocol;
 
@@ -37,8 +37,7 @@ public abstract class ViaListener {
      * @param uuid UUID object
      * @return The UserConnection
      */
-    @Nullable
-    protected UserConnection getUserConnection(UUID uuid) {
+    protected @Nullable UserConnection getUserConnection(UUID uuid) {
         return Via.getManager().getConnectionManager().getConnectedClient(uuid);
     }
 
diff --git a/common/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolManagerImpl.java b/common/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolManagerImpl.java
index 52da7f7c2..92da8f748 100644
--- a/common/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolManagerImpl.java
+++ b/common/src/main/java/us/myles/ViaVersion/api/protocol/ProtocolManagerImpl.java
@@ -23,7 +23,7 @@ import com.google.common.collect.Range;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Pair;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.MappingDataLoader;
@@ -210,9 +210,8 @@ public class ProtocolManagerImpl implements ProtocolManager {
         }
     }
 
-    @Nullable
     @Override
-    public List<ProtocolPathEntry> getProtocolPath(int clientVersion, int serverVersion) {
+    public @Nullable List<ProtocolPathEntry> getProtocolPath(int clientVersion, int serverVersion) {
         ProtocolPathKey protocolKey = new ProtocolPathKeyImpl(clientVersion, serverVersion);
         // Check cache
         List<ProtocolPathEntry> protocolList = pathCache.get(protocolKey);
@@ -237,8 +236,7 @@ public class ProtocolManagerImpl implements ProtocolManager {
      * @param serverVersion desired output version
      * @return path that has been generated, null if failed
      */
-    @Nullable
-    private List<ProtocolPathEntry> getProtocolPath(List<ProtocolPathEntry> current, int clientVersion, int serverVersion) {
+    private @Nullable List<ProtocolPathEntry> getProtocolPath(List<ProtocolPathEntry> current, int clientVersion, int serverVersion) {
         if (clientVersion == serverVersion) return null; // We're already there
         if (current.size() > maxProtocolPathSize) return null; // Fail safe, protocol too complicated.
 
@@ -282,9 +280,8 @@ public class ProtocolManagerImpl implements ProtocolManager {
         return shortest; // null if none found
     }
 
-    @Nullable
     @Override
-    public Protocol getProtocol(Class<? extends Protocol> protocolClass) {
+    public @Nullable Protocol getProtocol(Class<? extends Protocol> protocolClass) {
         return protocols.get(protocolClass);
     }
 
@@ -406,9 +403,8 @@ public class ProtocolManagerImpl implements ProtocolManager {
         }
     }
 
-    @Nullable
     @Override
-    public CompletableFuture<Void> getMappingLoaderFuture(Class<? extends Protocol> protocolClass) {
+    public @Nullable CompletableFuture<Void> getMappingLoaderFuture(Class<? extends Protocol> protocolClass) {
         mappingLoaderLock.readLock().lock();
         try {
             return mappingsLoaded ? null : mappingLoaderFutures.get(protocolClass);
diff --git a/common/src/main/java/us/myles/ViaVersion/api/rewriters/CommandRewriter.java b/common/src/main/java/us/myles/ViaVersion/api/rewriters/CommandRewriter.java
index 3d54a6d02..ee373f158 100644
--- a/common/src/main/java/us/myles/ViaVersion/api/rewriters/CommandRewriter.java
+++ b/common/src/main/java/us/myles/ViaVersion/api/rewriters/CommandRewriter.java
@@ -17,7 +17,7 @@
  */
 package us.myles.ViaVersion.api.rewriters;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.PacketWrapper;
 import us.myles.ViaVersion.api.protocol.ClientboundPacketType;
 import us.myles.ViaVersion.api.protocol.Protocol;
@@ -122,8 +122,7 @@ public abstract class CommandRewriter {
      * @param argumentType argument type
      * @return new argument type, or null if it should be removed
      */
-    @Nullable
-    protected String handleArgumentType(String argumentType) {
+    protected @Nullable String handleArgumentType(String argumentType) {
         return argumentType;
     }
 
diff --git a/common/src/main/java/us/myles/ViaVersion/api/rewriters/MetadataRewriter.java b/common/src/main/java/us/myles/ViaVersion/api/rewriters/MetadataRewriter.java
index ebebae675..d5d4a8702 100644
--- a/common/src/main/java/us/myles/ViaVersion/api/rewriters/MetadataRewriter.java
+++ b/common/src/main/java/us/myles/ViaVersion/api/rewriters/MetadataRewriter.java
@@ -19,7 +19,7 @@ package us.myles.ViaVersion.api.rewriters;
 
 import it.unimi.dsi.fastutil.ints.Int2IntMap;
 import it.unimi.dsi.fastutil.ints.Int2IntOpenHashMap;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.ParticleMappings;
 import us.myles.ViaVersion.api.data.UserConnection;
@@ -296,8 +296,7 @@ public abstract class MetadataRewriter {
      */
     protected abstract void handleMetadata(int entityId, @Nullable EntityType type, Metadata metadata, List<Metadata> metadatas, UserConnection connection) throws Exception;
 
-    @Nullable
-    protected Metadata getMetaByIndex(int index, List<Metadata> metadataList) {
+    protected @Nullable Metadata getMetaByIndex(int index, List<Metadata> metadataList) {
         for (Metadata metadata : metadataList) {
             if (metadata.getId() == index) {
                 return metadata;
diff --git a/common/src/main/java/us/myles/ViaVersion/api/rewriters/RegistryType.java b/common/src/main/java/us/myles/ViaVersion/api/rewriters/RegistryType.java
index b5db45613..236585f51 100644
--- a/common/src/main/java/us/myles/ViaVersion/api/rewriters/RegistryType.java
+++ b/common/src/main/java/us/myles/ViaVersion/api/rewriters/RegistryType.java
@@ -17,7 +17,7 @@
  */
 package us.myles.ViaVersion.api.rewriters;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.HashMap;
 import java.util.Map;
@@ -43,8 +43,7 @@ public enum RegistryType {
         return VALUES;
     }
 
-    @Nullable
-    public static RegistryType getByKey(String resourceKey) {
+    public static @Nullable RegistryType getByKey(String resourceKey) {
         return MAP.get(resourceKey);
     }
 
diff --git a/common/src/main/java/us/myles/ViaVersion/api/rewriters/StatisticsRewriter.java b/common/src/main/java/us/myles/ViaVersion/api/rewriters/StatisticsRewriter.java
index d2190da0e..f2449cf54 100644
--- a/common/src/main/java/us/myles/ViaVersion/api/rewriters/StatisticsRewriter.java
+++ b/common/src/main/java/us/myles/ViaVersion/api/rewriters/StatisticsRewriter.java
@@ -17,7 +17,7 @@
  */
 package us.myles.ViaVersion.api.rewriters;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.protocol.ClientboundPacketType;
 import us.myles.ViaVersion.api.protocol.Protocol;
 import us.myles.ViaVersion.api.remapper.PacketRemapper;
@@ -74,8 +74,7 @@ public class StatisticsRewriter {
         });
     }
 
-    @Nullable
-    protected IdRewriteFunction getRewriter(RegistryType type) {
+    protected @Nullable IdRewriteFunction getRewriter(RegistryType type) {
         switch (type) {
             case BLOCK:
                 return protocol.getMappingData().getBlockMappings() != null ? id -> protocol.getMappingData().getNewBlockId(id) : null;
@@ -87,8 +86,7 @@ public class StatisticsRewriter {
         throw new IllegalArgumentException("Unknown registry type in statistics packet: " + type);
     }
 
-    @Nullable
-    public RegistryType getRegistryTypeForStatistic(int statisticsId) {
+    public @Nullable RegistryType getRegistryTypeForStatistic(int statisticsId) {
         switch (statisticsId) {
             case 0:
                 return RegistryType.BLOCK;
diff --git a/common/src/main/java/us/myles/ViaVersion/api/rewriters/TagRewriter.java b/common/src/main/java/us/myles/ViaVersion/api/rewriters/TagRewriter.java
index 0f66f3f1f..a317095d9 100644
--- a/common/src/main/java/us/myles/ViaVersion/api/rewriters/TagRewriter.java
+++ b/common/src/main/java/us/myles/ViaVersion/api/rewriters/TagRewriter.java
@@ -19,7 +19,7 @@ package us.myles.ViaVersion.api.rewriters;
 
 import it.unimi.dsi.fastutil.ints.IntArrayList;
 import it.unimi.dsi.fastutil.ints.IntList;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.PacketWrapper;
 import us.myles.ViaVersion.api.data.MappingData;
 import us.myles.ViaVersion.api.protocol.ClientboundPacketType;
@@ -162,8 +162,7 @@ public class TagRewriter {
         }
     }
 
-    @Nullable
-    public List<TagData> getNewTags(RegistryType tagType) {
+    public @Nullable List<TagData> getNewTags(RegistryType tagType) {
         return newTags.get(tagType);
     }
 
@@ -171,8 +170,7 @@ public class TagRewriter {
         return newTags.computeIfAbsent(tagType, type -> new ArrayList<>());
     }
 
-    @Nullable
-    public IdRewriteFunction getRewriter(RegistryType tagType) {
+    public @Nullable IdRewriteFunction getRewriter(RegistryType tagType) {
         MappingData mappingData = protocol.getMappingData();
         switch (tagType) {
             case BLOCK:
diff --git a/common/src/main/java/us/myles/ViaVersion/api/storage/EntityTracker.java b/common/src/main/java/us/myles/ViaVersion/api/storage/EntityTracker.java
index 26ad5b845..11c71fc17 100644
--- a/common/src/main/java/us/myles/ViaVersion/api/storage/EntityTracker.java
+++ b/common/src/main/java/us/myles/ViaVersion/api/storage/EntityTracker.java
@@ -17,7 +17,7 @@
  */
 package us.myles.ViaVersion.api.storage;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.data.ExternalJoinGameListener;
 import us.myles.ViaVersion.api.data.StoredObject;
 import us.myles.ViaVersion.api.data.UserConnection;
@@ -48,8 +48,7 @@ public abstract class EntityTracker extends StoredObject implements ExternalJoin
         return clientEntityTypes.containsKey(entityId);
     }
 
-    @Nullable
-    public EntityType getEntity(int entityId) {
+    public @Nullable EntityType getEntity(int entityId) {
         return clientEntityTypes.get(entityId);
     }
 
diff --git a/common/src/main/java/us/myles/ViaVersion/commands/defaultsubs/PPSSubCmd.java b/common/src/main/java/us/myles/ViaVersion/commands/defaultsubs/PPSSubCmd.java
index f18b50f49..f0e21c029 100644
--- a/common/src/main/java/us/myles/ViaVersion/commands/defaultsubs/PPSSubCmd.java
+++ b/common/src/main/java/us/myles/ViaVersion/commands/defaultsubs/PPSSubCmd.java
@@ -23,7 +23,11 @@ import us.myles.ViaVersion.api.command.ViaSubCommand;
 import us.myles.ViaVersion.api.data.UserConnection;
 import us.myles.ViaVersion.api.protocol.ProtocolVersion;
 
-import java.util.*;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeMap;
 
 public class PPSSubCmd extends ViaSubCommand {
     @Override
diff --git a/common/src/main/java/us/myles/ViaVersion/handlers/ChannelHandlerContextWrapper.java b/common/src/main/java/us/myles/ViaVersion/handlers/ChannelHandlerContextWrapper.java
index 37c1c0489..e3dc7d228 100644
--- a/common/src/main/java/us/myles/ViaVersion/handlers/ChannelHandlerContextWrapper.java
+++ b/common/src/main/java/us/myles/ViaVersion/handlers/ChannelHandlerContextWrapper.java
@@ -19,7 +19,13 @@ package us.myles.ViaVersion.handlers;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufAllocator;
-import io.netty.channel.*;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelHandler;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelPipeline;
+import io.netty.channel.ChannelProgressivePromise;
+import io.netty.channel.ChannelPromise;
 import io.netty.util.Attribute;
 import io.netty.util.AttributeKey;
 import io.netty.util.concurrent.EventExecutor;
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_10to1_9_3/packets/InventoryPackets.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_10to1_9_3/packets/InventoryPackets.java
index 6e5bc2d9e..dd0e602b6 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_10to1_9_3/packets/InventoryPackets.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_10to1_9_3/packets/InventoryPackets.java
@@ -26,7 +26,8 @@ import us.myles.ViaVersion.protocols.protocol1_9_3to1_9_1_2.ServerboundPackets1_
 public class InventoryPackets {
 
     public static void register(Protocol1_10To1_9_3_4 protocol) {
-        ItemRewriter itemRewriter = new ItemRewriter(protocol, item -> {}, InventoryPackets::toServerItem);
+        ItemRewriter itemRewriter = new ItemRewriter(protocol, item -> {
+        }, InventoryPackets::toServerItem);
         itemRewriter.registerCreativeInvAction(ServerboundPackets1_9_3.CREATIVE_INVENTORY_ACTION, Type.ITEM);
     }
 
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_11_1to1_11/packets/InventoryPackets.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_11_1to1_11/packets/InventoryPackets.java
index a2dac473d..de4f436e8 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_11_1to1_11/packets/InventoryPackets.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_11_1to1_11/packets/InventoryPackets.java
@@ -26,7 +26,8 @@ import us.myles.ViaVersion.protocols.protocol1_9_3to1_9_1_2.ServerboundPackets1_
 public class InventoryPackets {
 
     public static void register(Protocol1_11_1To1_11 protocol) {
-        ItemRewriter itemRewriter = new ItemRewriter(protocol, item -> {}, InventoryPackets::toServerItem);
+        ItemRewriter itemRewriter = new ItemRewriter(protocol, item -> {
+        }, InventoryPackets::toServerItem);
         itemRewriter.registerCreativeInvAction(ServerboundPackets1_9_3.CREATIVE_INVENTORY_ACTION, Type.ITEM);
     }
 
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_11to1_10/packets/InventoryPackets.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_11to1_10/packets/InventoryPackets.java
index 3f0cf75bc..ce7371c03 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_11to1_10/packets/InventoryPackets.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_11to1_10/packets/InventoryPackets.java
@@ -23,10 +23,10 @@ import us.myles.ViaVersion.api.remapper.PacketHandler;
 import us.myles.ViaVersion.api.remapper.PacketRemapper;
 import us.myles.ViaVersion.api.rewriters.ItemRewriter;
 import us.myles.ViaVersion.api.type.Type;
-import us.myles.ViaVersion.protocols.protocol1_9_3to1_9_1_2.ClientboundPackets1_9_3;
-import us.myles.ViaVersion.protocols.protocol1_9_3to1_9_1_2.ServerboundPackets1_9_3;
 import us.myles.ViaVersion.protocols.protocol1_11to1_10.EntityIdRewriter;
 import us.myles.ViaVersion.protocols.protocol1_11to1_10.Protocol1_11To1_10;
+import us.myles.ViaVersion.protocols.protocol1_9_3to1_9_1_2.ClientboundPackets1_9_3;
+import us.myles.ViaVersion.protocols.protocol1_9_3to1_9_1_2.ServerboundPackets1_9_3;
 
 public class InventoryPackets {
 
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_12to1_11_1/packets/InventoryPackets.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_12to1_11_1/packets/InventoryPackets.java
index fa1c922c5..bd7e94bf5 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_12to1_11_1/packets/InventoryPackets.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_12to1_11_1/packets/InventoryPackets.java
@@ -24,11 +24,11 @@ import us.myles.ViaVersion.api.remapper.PacketHandler;
 import us.myles.ViaVersion.api.remapper.PacketRemapper;
 import us.myles.ViaVersion.api.rewriters.ItemRewriter;
 import us.myles.ViaVersion.api.type.Type;
-import us.myles.ViaVersion.protocols.protocol1_9_3to1_9_1_2.ClientboundPackets1_9_3;
 import us.myles.ViaVersion.protocols.protocol1_12to1_11_1.BedRewriter;
 import us.myles.ViaVersion.protocols.protocol1_12to1_11_1.Protocol1_12To1_11_1;
 import us.myles.ViaVersion.protocols.protocol1_12to1_11_1.ServerboundPackets1_12;
 import us.myles.ViaVersion.protocols.protocol1_12to1_11_1.providers.InventoryQuickMoveProvider;
+import us.myles.ViaVersion.protocols.protocol1_9_3to1_9_1_2.ClientboundPackets1_9_3;
 
 public class InventoryPackets {
 
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/Protocol1_13To1_12_2.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/Protocol1_13To1_12_2.java
index a6dbc1676..b4bf87c8b 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/Protocol1_13To1_12_2.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/Protocol1_13To1_12_2.java
@@ -119,7 +119,7 @@ public class Protocol1_13To1_12_2 extends Protocol<ClientboundPackets1_12_1, Cli
                         wrapper.write(Type.VAR_INT, 2); // Size
                         // Write root node
                         wrapper.write(Type.BYTE, (byte) 0); // Mark as command
-                        wrapper.write(Type.VAR_INT_ARRAY_PRIMITIVE, new int[] {1}); // 1 child at index 1
+                        wrapper.write(Type.VAR_INT_ARRAY_PRIMITIVE, new int[]{1}); // 1 child at index 1
 
                         // Write arg node
                         wrapper.write(Type.BYTE, (byte) (0x02 | 0x04 | 0x10)); // Mark as command
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/data/MappingData.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/data/MappingData.java
index 718f752fc..6fc0c9602 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/data/MappingData.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/data/MappingData.java
@@ -24,7 +24,7 @@ import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.reflect.TypeToken;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.MappingDataLoader;
 import us.myles.ViaVersion.api.data.Mappings;
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/providers/blockentities/BannerHandler.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/providers/blockentities/BannerHandler.java
index 992eeca4b..39681b8b8 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/providers/blockentities/BannerHandler.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_13to1_12_2/providers/blockentities/BannerHandler.java
@@ -17,7 +17,12 @@
  */
 package us.myles.ViaVersion.protocols.protocol1_13to1_12_2.providers.blockentities;
 
-import com.github.steveice10.opennbt.tag.builtin.*;
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import com.github.steveice10.opennbt.tag.builtin.IntTag;
+import com.github.steveice10.opennbt.tag.builtin.ListTag;
+import com.github.steveice10.opennbt.tag.builtin.NumberTag;
+import com.github.steveice10.opennbt.tag.builtin.StringTag;
+import com.github.steveice10.opennbt.tag.builtin.Tag;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.UserConnection;
 import us.myles.ViaVersion.api.minecraft.Position;
@@ -64,7 +69,7 @@ public class BannerHandler implements BlockEntityProvider.BlockEntityHandler {
                 if (pattern instanceof CompoundTag) {
                     Tag c = ((CompoundTag) pattern).get("Color");
                     if (c instanceof IntTag) {
-                        ((IntTag)c).setValue(15 - (int) c.getValue()); // Invert color id
+                        ((IntTag) c).setValue(15 - (int) c.getValue()); // Invert color id
                     }
                 }
             }
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_14to1_13_2/data/CommandRewriter1_14.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_14to1_13_2/data/CommandRewriter1_14.java
index 1d986f5a9..218760f37 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_14to1_13_2/data/CommandRewriter1_14.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_14to1_13_2/data/CommandRewriter1_14.java
@@ -17,7 +17,7 @@
  */
 package us.myles.ViaVersion.protocols.protocol1_14to1_13_2.data;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.protocol.Protocol;
 import us.myles.ViaVersion.api.rewriters.CommandRewriter;
 
@@ -28,8 +28,7 @@ public class CommandRewriter1_14 extends CommandRewriter {
     }
 
     @Override
-    @Nullable
-    protected String handleArgumentType(String argumentType) {
+    protected @Nullable String handleArgumentType(String argumentType) {
         if (argumentType.equals("minecraft:nbt")) {
             return "minecraft:nbt_compound_tag";
         }
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_14to1_13_2/packets/InventoryPackets.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_14to1_13_2/packets/InventoryPackets.java
index 6aec84ea0..76ee83a71 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_14to1_13_2/packets/InventoryPackets.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_14to1_13_2/packets/InventoryPackets.java
@@ -17,7 +17,11 @@
  */
 package us.myles.ViaVersion.protocols.protocol1_14to1_13_2.packets;
 
-import com.github.steveice10.opennbt.tag.builtin.*;
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import com.github.steveice10.opennbt.tag.builtin.DoubleTag;
+import com.github.steveice10.opennbt.tag.builtin.ListTag;
+import com.github.steveice10.opennbt.tag.builtin.StringTag;
+import com.github.steveice10.opennbt.tag.builtin.Tag;
 import com.google.common.collect.Sets;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_15to1_14_4/data/MappingData.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_15to1_14_4/data/MappingData.java
index 7ccf3612e..0bc5883f6 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_15to1_14_4/data/MappingData.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_15to1_14_4/data/MappingData.java
@@ -18,7 +18,7 @@
 package us.myles.ViaVersion.protocols.protocol1_15to1_14_4.data;
 
 import com.google.gson.JsonObject;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.data.Mappings;
 
 public class MappingData extends us.myles.ViaVersion.api.data.MappingData {
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_16to1_15_2/packets/EntityPackets.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_16to1_15_2/packets/EntityPackets.java
index de8507725..869b8942e 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_16to1_15_2/packets/EntityPackets.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_16to1_15_2/packets/EntityPackets.java
@@ -109,7 +109,7 @@ public class EntityPackets {
         CompoundTag tag = new CompoundTag();
         tag.put("piglin_safe", new ByteTag((byte) 1));
         tag.put("natural", new ByteTag((byte) 0));
-        tag.put("ambient_light",new FloatTag( 0.1F));
+        tag.put("ambient_light", new FloatTag(0.1F));
         tag.put("infiniburn", new StringTag("minecraft:infiniburn_nether"));
         tag.put("respawn_anchor_works", new ByteTag((byte) 1));
         tag.put("has_skylight", new ByteTag((byte) 0));
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_17to1_16_4/Protocol1_17To1_16_4.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_17to1_16_4/Protocol1_17To1_16_4.java
index b9e8594c3..f180350ec 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_17to1_16_4/Protocol1_17To1_16_4.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_17to1_16_4/Protocol1_17To1_16_4.java
@@ -17,7 +17,7 @@
  */
 package us.myles.ViaVersion.protocols.protocol1_17to1_16_4;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.data.MappingData;
 import us.myles.ViaVersion.api.data.UserConnection;
@@ -228,8 +228,7 @@ public class Protocol1_17To1_16_4 extends Protocol<ClientboundPackets1_16_2, Cli
     }
 
     @Override
-    @Nullable
-    public MappingData getMappingData() {
+    public @Nullable MappingData getMappingData() {
         return MAPPINGS;
     }
 }
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_17to1_16_4/storage/BiomeStorage.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_17to1_16_4/storage/BiomeStorage.java
index 24b631237..d0e839373 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_17to1_16_4/storage/BiomeStorage.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_17to1_16_4/storage/BiomeStorage.java
@@ -17,7 +17,7 @@
  */
 package us.myles.ViaVersion.protocols.protocol1_17to1_16_4.storage;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.data.StoredObject;
 import us.myles.ViaVersion.api.data.UserConnection;
 
@@ -33,8 +33,7 @@ public class BiomeStorage extends StoredObject {
         super(user);
     }
 
-    @Nullable
-    public String getWorld() {
+    public @Nullable String getWorld() {
         return world;
     }
 
@@ -42,8 +41,7 @@ public class BiomeStorage extends StoredObject {
         this.world = world;
     }
 
-    @Nullable
-    public int[] getBiomes(int x, int z) {
+    public int @Nullable [] getBiomes(int x, int z) {
         return chunkBiomes.get(getChunkSectionIndex(x, z));
     }
 
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/packets/EntityPackets.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/packets/EntityPackets.java
index f5683d34a..5ab7b5e81 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/packets/EntityPackets.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/packets/EntityPackets.java
@@ -343,7 +343,7 @@ public class EntityPackets {
                 handler(new PacketHandler() {
                     @Override
                     public void handle(PacketWrapper wrapper) throws Exception {
-                        if(wrapper.get(Type.UNSIGNED_BYTE, 0) == 3) {
+                        if (wrapper.get(Type.UNSIGNED_BYTE, 0) == 3) {
                             wrapper.cancel();
                         }
                     }
diff --git a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/types/Chunk1_9to1_8Type.java b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/types/Chunk1_9to1_8Type.java
index e2a46f215..b6eee796c 100644
--- a/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/types/Chunk1_9to1_8Type.java
+++ b/common/src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/types/Chunk1_9to1_8Type.java
@@ -21,6 +21,7 @@ import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
 import io.netty.buffer.ByteBuf;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.api.minecraft.chunks.Chunk;
+import us.myles.ViaVersion.api.minecraft.chunks.Chunk1_8;
 import us.myles.ViaVersion.api.minecraft.chunks.ChunkSection;
 import us.myles.ViaVersion.api.type.PartialType;
 import us.myles.ViaVersion.api.type.Type;
@@ -28,7 +29,6 @@ import us.myles.ViaVersion.api.type.types.minecraft.BaseChunkType;
 import us.myles.ViaVersion.api.type.types.version.Types1_8;
 import us.myles.ViaVersion.api.type.types.version.Types1_9;
 import us.myles.ViaVersion.protocols.protocol1_10to1_9_3.Protocol1_10To1_9_3_4;
-import us.myles.ViaVersion.api.minecraft.chunks.Chunk1_8;
 import us.myles.ViaVersion.protocols.protocol1_9to1_8.storage.ClientChunks;
 
 import java.util.ArrayList;
diff --git a/common/src/main/java/us/myles/ViaVersion/update/UpdateUtil.java b/common/src/main/java/us/myles/ViaVersion/update/UpdateUtil.java
index 02bd0e3ad..deaf4ee44 100644
--- a/common/src/main/java/us/myles/ViaVersion/update/UpdateUtil.java
+++ b/common/src/main/java/us/myles/ViaVersion/update/UpdateUtil.java
@@ -19,7 +19,7 @@ package us.myles.ViaVersion.update;
 
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParseException;
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import us.myles.ViaVersion.api.Via;
 import us.myles.ViaVersion.util.GsonUtil;
 
@@ -57,8 +57,7 @@ public class UpdateUtil {
         });
     }
 
-    @Nullable
-    private static String getUpdateMessage(boolean console) {
+    private static @Nullable String getUpdateMessage(boolean console) {
         if (Via.getPlatform().getPluginVersion().equals("${version}")) {
             return "You are using a debug/custom version, consider updating.";
         }
@@ -89,8 +88,7 @@ public class UpdateUtil {
         return null;
     }
 
-    @Nullable
-    private static String getNewestVersion() {
+    private static @Nullable String getNewestVersion() {
         try {
             URL url = new URL(URL + PLUGIN + LATEST_VERSION + "?" + System.currentTimeMillis());
             HttpURLConnection connection = (HttpURLConnection) url.openConnection();
diff --git a/common/src/main/java/us/myles/ViaVersion/util/CommentStore.java b/common/src/main/java/us/myles/ViaVersion/util/CommentStore.java
index 96a7b89ef..0cb5ee939 100644
--- a/common/src/main/java/us/myles/ViaVersion/util/CommentStore.java
+++ b/common/src/main/java/us/myles/ViaVersion/util/CommentStore.java
@@ -22,7 +22,11 @@ import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.google.common.io.CharStreams;
 
-import java.io.*;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
diff --git a/common/src/main/java/us/myles/ViaVersion/util/Config.java b/common/src/main/java/us/myles/ViaVersion/util/Config.java
index 12010816d..e71a9d7dc 100644
--- a/common/src/main/java/us/myles/ViaVersion/util/Config.java
+++ b/common/src/main/java/us/myles/ViaVersion/util/Config.java
@@ -17,13 +17,17 @@
  */
 package us.myles.ViaVersion.util;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import org.yaml.snakeyaml.DumperOptions;
 import org.yaml.snakeyaml.Yaml;
 import org.yaml.snakeyaml.representer.Representer;
 import us.myles.ViaVersion.api.configuration.ConfigurationProvider;
 
-import java.io.*;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -142,8 +146,7 @@ public abstract class Config implements ConfigurationProvider {
         return this.config;
     }
 
-    @Nullable
-    public <T> T get(String key, Class<T> clazz, T def) {
+    public @Nullable <T> T get(String key, Class<T> clazz, T def) {
         Object o = this.config.get(key);
         if (o != null) {
             return (T) o;
@@ -161,8 +164,7 @@ public abstract class Config implements ConfigurationProvider {
         }
     }
 
-    @Nullable
-    public String getString(String key, @Nullable String def) {
+    public @Nullable String getString(String key, @Nullable String def) {
         final Object o = this.config.get(key);
         if (o != null) {
             return (String) o;
diff --git a/sponge/src/main/java/us/myles/ViaVersion/sponge/commands/SpongeCommandHandler.java b/sponge/src/main/java/us/myles/ViaVersion/sponge/commands/SpongeCommandHandler.java
index 649b2c73c..7398688d3 100644
--- a/sponge/src/main/java/us/myles/ViaVersion/sponge/commands/SpongeCommandHandler.java
+++ b/sponge/src/main/java/us/myles/ViaVersion/sponge/commands/SpongeCommandHandler.java
@@ -17,7 +17,7 @@
  */
 package us.myles.ViaVersion.sponge.commands;
 
-import org.jetbrains.annotations.Nullable;
+import org.checkerframework.checker.nullness.qual.Nullable;
 import org.spongepowered.api.command.CommandCallable;
 import org.spongepowered.api.command.CommandException;
 import org.spongepowered.api.command.CommandResult;