diff --git a/esphome/components/json/json_util.cpp b/esphome/components/json/json_util.cpp
index 10179c9954..2bd8112255 100644
--- a/esphome/components/json/json_util.cpp
+++ b/esphome/components/json/json_util.cpp
@@ -23,13 +23,13 @@ std::string build_json(const json_build_t &f) {
 #ifdef USE_ESP8266
   const size_t free_heap = ESP.getMaxFreeBlockSize();  // NOLINT(readability-static-accessed-through-instance)
 #elif defined(USE_ESP32)
-  const size_t free_heap = heap_caps_get_largest_free_block(MALLOC_CAP_INTERNAL);
+  const size_t free_heap = heap_caps_get_largest_free_block(MALLOC_CAP_8BIT);
 #endif
 
-  const size_t request_size = std::min(free_heap - 2048, (size_t) 5120);
+  const size_t request_size = std::min(free_heap, (size_t) 512);
 
   DynamicJsonDocument json_document(request_size);
-  if (json_document.memoryPool().buffer() == nullptr) {
+  if (json_document.capacity() == 0) {
     ESP_LOGE(TAG, "Could not allocate memory for JSON document! Requested %u bytes, largest free heap block: %u bytes",
              request_size, free_heap);
     return "{}";
@@ -37,7 +37,7 @@ std::string build_json(const json_build_t &f) {
   JsonObject root = json_document.to<JsonObject>();
   f(root);
   json_document.shrinkToFit();
-
+  ESP_LOGV(TAG, "Size after shrink %u bytes", json_document.capacity());
   std::string output;
   serializeJson(json_document, output);
   return output;
@@ -51,13 +51,13 @@ void parse_json(const std::string &data, const json_parse_t &f) {
 #ifdef USE_ESP8266
   const size_t free_heap = ESP.getMaxFreeBlockSize();  // NOLINT(readability-static-accessed-through-instance)
 #elif defined(USE_ESP32)
-  const size_t free_heap = heap_caps_get_largest_free_block(MALLOC_CAP_INTERNAL);
+  const size_t free_heap = heap_caps_get_largest_free_block(MALLOC_CAP_8BIT);
 #endif
   bool pass = false;
-  size_t request_size = std::min(free_heap - 2048, (size_t)(data.size() * 1.5));
+  size_t request_size = std::min(free_heap, (size_t)(data.size() * 1.5));
   do {
     DynamicJsonDocument json_document(request_size);
-    if (json_document.memoryPool().buffer() == nullptr) {
+    if (json_document.capacity() == 0) {
       ESP_LOGE(TAG, "Could not allocate memory for JSON document! Requested %u bytes, free heap: %u", request_size,
                free_heap);
       return;