diff --git a/README.md b/README.md
index f4d5978..4659d70 100644
--- a/README.md
+++ b/README.md
@@ -495,7 +495,7 @@ ESPUI includes a range of advanced features that can customise your UIs.
 
 ### Dynamic Visibility
 
-Cotrols can be made visible or invisible at runtime with the `updateVisibility()` function.
+Controls can be made visible or invisible at runtime with the `updateVisibility()` function.
 
 ```
 ESPUI.updateVisibility(controlId, false);
diff --git a/src/ESPUI.cpp b/src/ESPUI.cpp
index abbe40a..90f84e3 100644
--- a/src/ESPUI.cpp
+++ b/src/ESPUI.cpp
@@ -13,6 +13,61 @@
 #include "dataTabbedcontentJS.h"
 #include "dataZeptoJS.h"
 
+#if ESP8266
+#include <umm_malloc/umm_heap_select.h>
+#endif
+
+static String heapInfo (const __FlashStringHelper* mode)
+{
+#if ESP8266
+
+    uint32_t hfree;
+    uint32_t hmax;
+    uint8_t hfrag;
+    String result;
+    result.reserve(128);
+
+#ifdef UMM_HEAP_IRAM
+    // here esp8266 is configurerd to use an extra 16KB (i)ram
+    {
+        HeapSelectIram useInstructionRamHere;
+        ESP.getHeapStats(&hfree, &hmax, &hfrag);
+    }
+    result += F("IRAM: free: ");
+    result += hfree;
+    result += F(" max: ");
+    result += hmax;
+    result += F(" frag: ");
+    result += hfrag;
+    result += "%\n";
+#endif // !UMM_HEAP_IRAM
+    {
+        HeapSelectDram useRegularRamHere;
+        ESP.getHeapStats(&hfree, &hmax, &hfrag);
+    }
+    result += F("DRAM: free: ");
+    result += hfree;
+    result += F(" max: ");
+    result += hmax;
+    result += F(" frag: ");
+    result += hfrag;
+    result += "%\n";
+
+#else // !ESP8266
+
+    result += ESP.getFreeHeap();
+    result += ' ';
+
+#endif // !ESP8266
+
+    result += mode;
+
+    return result;
+}
+
+
+
+
 // ################# LITTLEFS functions
 #if defined(ESP32)
 void listDir(const char* dirname, uint8_t levels)
@@ -1260,7 +1315,8 @@ void ESPUIClass::beginLITTLEFS(const char* _title, const char* username, const c
             return request->requestAuthentication();
         }
 
-        request->send(200, "text/plain", String(ESP.getFreeHeap()) + " In LITTLEFS mode");
+        request->send(200, "text/plain", heapInfo(F("In LITTLEFS mode")));
+
     });
 
     server->onNotFound([this](AsyncWebServerRequest* request) {
@@ -1418,7 +1474,7 @@ void ESPUIClass::begin(const char* _title, const char* username, const char* pas
             return request->requestAuthentication();
         }
 
-        request->send(200, "text/plain", String(ESP.getFreeHeap()) + " In Memorymode");
+        request->send(200, "text/plain", heapInfo(F("In Memorymode")));
     });
 
     server->onNotFound([this](AsyncWebServerRequest* request) {
diff --git a/src/ESPUI.h b/src/ESPUI.h
index fb42039..878097f 100644
--- a/src/ESPUI.h
+++ b/src/ESPUI.h
@@ -87,20 +87,20 @@ enum Verbosity : uint8_t
 class ESPUIClass
 {
 public:
+
+#ifdef ESP32
     ESPUIClass()
     {
-        verbosity = Verbosity::Quiet;
-        jsonUpdateDocumentSize = 2000;
-        jsonInitialDocumentSize = 8000;
-        sliderContinuous = false;
-#ifdef ESP32
         ControlsSemaphore = xSemaphoreCreateMutex();
         xSemaphoreGive(ControlsSemaphore);
-#endif // def ESP32
     }
-    unsigned int jsonUpdateDocumentSize;
-    unsigned int jsonInitialDocumentSize;
-    bool sliderContinuous;
+    SemaphoreHandle_t ControlsSemaphore = NULL;
+#endif // def ESP32
+
+    unsigned int jsonUpdateDocumentSize = 2000;
+    unsigned int jsonInitialDocumentSize = 8000;
+    unsigned int jsonChunkNumberMax = 0;
+    bool sliderContinuous = false;
     void onWsEvent(AsyncWebSocket* server, AsyncWebSocketClient* client, AwsEventType type, void* arg, uint8_t* data, size_t len);
 	bool captivePortal = true;
 
@@ -205,17 +205,13 @@ public:
     void jsonReload();
     void jsonDom(uint16_t startidx, AsyncWebSocketClient* client = nullptr, bool Updating = false);
 
-    Verbosity verbosity;
+    Verbosity verbosity = Verbosity::Quiet;
     AsyncWebServer* server;
 
 protected:
     friend class ESPUIclient;
     friend class ESPUIcontrol;
 
-#ifdef ESP32
-    SemaphoreHandle_t ControlsSemaphore = NULL;
-#endif // def ESP32
-
     void        RemoveToBeDeletedControls();
 
     AsyncWebSocket* ws;
diff --git a/src/ESPUIclient.cpp b/src/ESPUIclient.cpp
index 9b7d561..9bce217 100644
--- a/src/ESPUIclient.cpp
+++ b/src/ESPUIclient.cpp
@@ -2,6 +2,42 @@
 #include "ESPUIclient.h"
 #include "ESPUIcontrol.h"
 
+// JSONSlave:
+// helper to process exact JSON serialization size
+// it takes ~2ms on esp8266 and avoid large String reallocation which is really worth the cost
+class JSONSlave: public Print
+{
+public:
+    size_t write (uint8_t c) override { counter++; return 1; }
+    size_t write (const uint8_t* buf, size_t count) override { counter += count; return count; }
+    size_t get_counter () { return counter; }
+
+    static size_t serializedSize (JsonDocument& doc)
+    {
+        JSONSlave counter;
+        serializeJson(doc, counter);
+        return counter.get_counter();
+    }
+
+    static size_t serialize (JsonDocument& doc, String& str)
+    {
+        size_t s = serializedSize(doc) + 10; // 10 is paranoid
+        str.reserve(s);
+        serializeJson(doc, str);
+        return s;
+    }
+
+    static String toString (JsonDocument& doc)
+    {
+        String str;
+        serialize(doc, str);
+        return str;
+    }
+
+protected:
+    size_t counter = 0;
+};
+
 ESPUIclient::ESPUIclient(AsyncWebSocketClient * _client):
     client(_client)
 {
@@ -309,7 +345,7 @@ uint32_t ESPUIclient::prepareJSONChunk(uint16_t startindex,
             elementcount++;
             control->MarshalControl(item, InUpdateMode);
             
-            if (rootDoc.overflowed())
+            if (rootDoc.overflowed() || (ESPUI.jsonChunkNumberMax > 0 && (elementcount % ESPUI.jsonChunkNumberMax) == 0))
             {
                 // String("prepareJSONChunk: too much data in the message. Remove the last entry");
                 if (1 == elementcount)
@@ -407,9 +443,8 @@ bool ESPUIclient::SendControlsToClient(uint16_t startidx,
                 if (ESPUI.verbosity >= Verbosity::VerboseJSON)
                 {
                     Serial.println(F("ESPUIclient:SendControlsToClient: Sending elements --------->"));
-                    String json;
-                    serializeJson(document, json);
-                    Serial.println(json);
+                    serializeJson(document, Serial);
+                    Serial.println();
                 }
             #endif
 
@@ -454,10 +489,7 @@ bool ESPUIclient::SendJsonDocToWebSocket(DynamicJsonDocument& document)
             break;
         }
 
-        String json;
-        json.reserve(document.size() / 2);
-        json.clear();
-        serializeJson(document, json);
+        String json = JSONSlave::toString(document);
 
         #if defined(DEBUG_ESPUI)
             if (ESPUI.verbosity >= Verbosity::VerboseJSON)