diff --git a/src/App/Services/MobileI18nService.cs b/src/App/Services/MobileI18nService.cs
index feed8db2b..ba2c3ed95 100644
--- a/src/App/Services/MobileI18nService.cs
+++ b/src/App/Services/MobileI18nService.cs
@@ -53,12 +53,12 @@ namespace Bit.App.Services
             Thread.CurrentThread.CurrentUICulture = Culture;
         }
 
-        public string T(string id, string p1, string p2, string p3)
+        public string T(string id, string p1 = null, string p2 = null, string p3 = null)
         {
             return Translate(id, p1, p2, p3);
         }
 
-        public string Translate(string id, string p1, string p2, string p3)
+        public string Translate(string id, string p1 = null, string p2 = null, string p3 = null)
         {
             if(string.IsNullOrWhiteSpace(id))
             {
diff --git a/src/Core/Abstractions/II18nService.cs b/src/Core/Abstractions/II18nService.cs
index 80d6a6c7f..69e1b8fe2 100644
--- a/src/Core/Abstractions/II18nService.cs
+++ b/src/Core/Abstractions/II18nService.cs
@@ -7,7 +7,7 @@ namespace Bit.Core.Abstractions
     {
         CultureInfo Culture { get; set; }
         StringComparer StringComparer { get; }
-        string T(string id, string p1, string p2, string p3);
-        string Translate(string id, string p1, string p2, string p3);
+        string T(string id, string p1 = null, string p2 = null, string p3 = null);
+        string Translate(string id, string p1 = null, string p2 = null, string p3 = null);
     }
 }
\ No newline at end of file
diff --git a/src/Core/Models/Domain/Folder.cs b/src/Core/Models/Domain/Folder.cs
index 8bf6dd374..bec956cbd 100644
--- a/src/Core/Models/Domain/Folder.cs
+++ b/src/Core/Models/Domain/Folder.cs
@@ -24,9 +24,9 @@ namespace Bit.Core.Models.Domain
         public CipherString Name { get; set; }
         public DateTime RevisionDate { get; set; }
 
-        public Task<FolderView> DecryptAsync(string orgId)
+        public Task<FolderView> DecryptAsync()
         {
-            return DecryptObjAsync(new FolderView(this), this, new HashSet<string> { "Name" }, orgId);
+            return DecryptObjAsync(new FolderView(this), this, new HashSet<string> { "Name" }, null);
         }
     }
 }
diff --git a/src/Core/Services/FolderService.cs b/src/Core/Services/FolderService.cs
new file mode 100644
index 000000000..99c1efb0b
--- /dev/null
+++ b/src/Core/Services/FolderService.cs
@@ -0,0 +1,259 @@
+using Bit.Core.Abstractions;
+using Bit.Core.Enums;
+using Bit.Core.Exceptions;
+using Bit.Core.Models.Data;
+using Bit.Core.Models.Domain;
+using Bit.Core.Models.Request;
+using Bit.Core.Models.Response;
+using Bit.Core.Models.View;
+using Bit.Core.Utilities;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Net.Http;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+
+namespace Bit.Core.Services
+{
+    public class FolderService
+    {
+        private const string Keys_CiphersFormat = "ciphers_{0}";
+        private const string Keys_FoldersFormat = "folders_{0}";
+        private const string NestingDelimiter = "/";
+
+        private List<FolderView> _decryptedFolderCache;
+        private readonly ICryptoService _cryptoService;
+        private readonly IUserService _userService;
+        private readonly IApiService _apiService;
+        private readonly IStorageService _storageService;
+        private readonly II18nService _i18nService;
+        private readonly ICipherService _cipherService;
+
+        public FolderService(
+            ICryptoService cryptoService,
+            IUserService userService,
+            IApiService apiService,
+            IStorageService storageService,
+            II18nService i18nService,
+            ICipherService cipherService)
+        {
+            _cryptoService = cryptoService;
+            _userService = userService;
+            _apiService = apiService;
+            _storageService = storageService;
+            _i18nService = i18nService;
+            _cipherService = cipherService;
+        }
+
+        public void ClearCache()
+        {
+            _decryptedFolderCache = null;
+        }
+
+        public async Task<Folder> EncryptAsync(FolderView model, SymmetricCryptoKey key = null)
+        {
+            var folder = new Folder
+            {
+                Id = model.Id,
+                Name = await _cryptoService.EncryptAsync(model.Name, key)
+            };
+            return folder;
+        }
+
+        public async Task<Folder> GetAsync(string id)
+        {
+            var userId = await _userService.GetUserIdAsync();
+            var folders = await _storageService.GetAsync<Dictionary<string, FolderData>>(
+                string.Format(Keys_FoldersFormat, userId));
+            if(!folders?.ContainsKey(id) ?? true)
+            {
+                return null;
+            }
+            return new Folder(folders[id]);
+        }
+
+        public async Task<List<Folder>> GetAllAsync()
+        {
+            var userId = await _userService.GetUserIdAsync();
+            var folders = await _storageService.GetAsync<Dictionary<string, FolderData>>(
+                string.Format(Keys_CiphersFormat, userId));
+            var response = folders.Select(f => new Folder(f.Value));
+            return response.ToList();
+        }
+
+        // TODO: sequentialize?
+        public async Task<List<FolderView>> GetAllDecryptedAsync()
+        {
+            if(_decryptedFolderCache != null)
+            {
+                return _decryptedFolderCache;
+            }
+            var hashKey = await _cryptoService.HasKeyAsync();
+            if(!hashKey)
+            {
+                throw new Exception("No key.");
+            }
+            var decFolders = new List<FolderView>();
+            var tasks = new List<Task>();
+            var folders = await GetAllAsync();
+            foreach(var folder in folders)
+            {
+                tasks.Add(folder.DecryptAsync().ContinueWith(async f => decFolders.Add(await f)));
+            }
+            await Task.WhenAll(tasks);
+            decFolders = decFolders.OrderBy(f => f, new FolderLocaleComparer(_i18nService)).ToList();
+
+            var noneFolder = new FolderView
+            {
+                Name = _i18nService.T("noneFolder")
+            };
+            decFolders.Add(noneFolder);
+
+            _decryptedFolderCache = decFolders;
+            return _decryptedFolderCache;
+        }
+
+        // TODO: nested stuff
+
+        public async Task SaveWithServerAsync(Folder folder)
+        {
+            var request = new FolderRequest(folder);
+            FolderResponse response;
+            if(folder.Id == null)
+            {
+                response = await _apiService.PostFolderAsync(request);
+                folder.Id = response.Id;
+            }
+            else
+            {
+                response = await _apiService.PutFolderAsync(folder.Id, request);
+            }
+            var userId = await _userService.GetUserIdAsync();
+            var data = new FolderData(response, userId);
+            await UpsertAsync(data);
+        }
+
+        public async Task UpsertAsync(FolderData folder)
+        {
+            var userId = await _userService.GetUserIdAsync();
+            var storageKey = string.Format(Keys_FoldersFormat, userId);
+            var folders = await _storageService.GetAsync<Dictionary<string, FolderData>>(storageKey);
+            if(folders == null)
+            {
+                folders = new Dictionary<string, FolderData>();
+            }
+            if(!folders.ContainsKey(folder.Id))
+            {
+                folders.Add(folder.Id, null);
+            }
+            folders[folder.Id] = folder;
+            await _storageService.SaveAsync(storageKey, folders);
+            _decryptedFolderCache = null;
+        }
+
+        public async Task UpsertAsync(List<FolderData> folder)
+        {
+            var userId = await _userService.GetUserIdAsync();
+            var storageKey = string.Format(Keys_FoldersFormat, userId);
+            var folders = await _storageService.GetAsync<Dictionary<string, FolderData>>(storageKey);
+            if(folders == null)
+            {
+                folders = new Dictionary<string, FolderData>();
+            }
+            foreach(var f in folder)
+            {
+                if(!folders.ContainsKey(f.Id))
+                {
+                    folders.Add(f.Id, null);
+                }
+                folders[f.Id] = f;
+            }
+            await _storageService.SaveAsync(storageKey, folders);
+            _decryptedFolderCache = null;
+        }
+
+        public async Task ReplaceAsync(Dictionary<string, FolderData> folders)
+        {
+            var userId = await _userService.GetUserIdAsync();
+            await _storageService.SaveAsync(string.Format(Keys_FoldersFormat, userId), folders);
+            _decryptedFolderCache = null;
+        }
+
+        public async Task ClearAsync(string userId)
+        {
+            await _storageService.RemoveAsync(string.Format(Keys_FoldersFormat, userId));
+            _decryptedFolderCache = null;
+        }
+
+        public async Task DeleteAsync(string id)
+        {
+            var userId = await _userService.GetUserIdAsync();
+            var folderKey = string.Format(Keys_FoldersFormat, userId);
+            var folders = await _storageService.GetAsync<Dictionary<string, FolderData>>(folderKey);
+            if(folders == null || !folders.ContainsKey(id))
+            {
+                return;
+            }
+            folders.Remove(id);
+            await _storageService.SaveAsync(folderKey, folders);
+            _decryptedFolderCache = null;
+
+            // Items in a deleted folder are re-assigned to "No Folder"
+            var ciphers = await _storageService.GetAsync<Dictionary<string, CipherData>>(
+                string.Format(Keys_CiphersFormat, userId));
+            if(ciphers != null)
+            {
+                var updates = new List<CipherData>();
+                foreach(var c in ciphers)
+                {
+                    if(c.Value.FolderId == id)
+                    {
+                        c.Value.FolderId = null;
+                        updates.Add(c.Value);
+                    }
+                }
+                if(updates.Any())
+                {
+                    await _cipherService.UpsertAsync(updates);
+                }
+            }
+        }
+
+        public async Task DeleteWithServerAsync(string id)
+        {
+            await _apiService.DeleteFolderAsync(id);
+            await DeleteAsync(id);
+        }
+
+        private class FolderLocaleComparer : IComparer<FolderView>
+        {
+            private readonly II18nService _i18nService;
+
+            public FolderLocaleComparer(II18nService i18nService)
+            {
+                _i18nService = i18nService;
+            }
+
+            public int Compare(FolderView a, FolderView b)
+            {
+                var aName = a.Name;
+                var bName = b.Name;
+                if(aName == null && bName != null)
+                {
+                    return -1;
+                }
+                if(aName != null && bName == null)
+                {
+                    return 1;
+                }
+                if(aName == null && bName == null)
+                {
+                    return 0;
+                }
+                return _i18nService.StringComparer.Compare(aName, bName);
+            }
+        }
+    }
+}