diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 57d7d68f0..ddb4bc8b2 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -54,6 +54,7 @@ The following binary downloads have been compiled with ESP8266/Arduino library c
 
 ### Version 8.3.1.7
 
+- Remove Arduino ESP8266 Core support for versions before 2.7.1
 - Change to limited support of Arduino IDE as an increasing amount of features cannot be compiled with Arduino IDE
 - Change IRremoteESP8266 library from v2.7.6 to v2.7.8
 - Change Adafruit_SGP30 library from v1.0.3 to v1.2.0 (#8519)
diff --git a/tasmota/CHANGELOG.md b/tasmota/CHANGELOG.md
index e397e2cc3..b67609a80 100644
--- a/tasmota/CHANGELOG.md
+++ b/tasmota/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ### 8.3.1.7 20200716
 
+- Remove Arduino ESP8266 Core support for versions before 2.7.1
 - Change to limited support of Arduino IDE as an increasing amount of features cannot be compiled with Arduino IDE
 
 ### 8.3.1.6 20200617
diff --git a/tasmota/WiFiClientSecureLightBearSSL.cpp b/tasmota/WiFiClientSecureLightBearSSL.cpp
index 0d69ff810..7b92d4b6e 100755
--- a/tasmota/WiFiClientSecureLightBearSSL.cpp
+++ b/tasmota/WiFiClientSecureLightBearSSL.cpp
@@ -50,9 +50,7 @@ extern "C" {
 #include "c_types.h"
 
 #include <core_version.h>
-#ifndef ARDUINO_ESP8266_RELEASE_2_5_2
 #undef DEBUG_TLS
-#endif
 
 #ifdef DEBUG_TLS
 #include "coredecls.h"
@@ -255,24 +253,14 @@ void WiFiClientSecure_light::setBufferSizes(int recv, int xmit) {
 }
 
 bool WiFiClientSecure_light::stop(unsigned int maxWaitMs) {
-#ifdef ARDUINO_ESP8266_RELEASE_2_4_2
-  WiFiClient::stop(); // calls our virtual flush()
-  _freeSSL();
-	return true;
-#else
   bool ret = WiFiClient::stop(maxWaitMs); // calls our virtual flush()
   _freeSSL();
   return ret;
-#endif
 }
 
 bool WiFiClientSecure_light::flush(unsigned int maxWaitMs) {
   (void) _run_until(BR_SSL_SENDAPP);
-#ifdef ARDUINO_ESP8266_RELEASE_2_4_2
-  WiFiClient::flush();
-#else
   return WiFiClient::flush(maxWaitMs);
-#endif
 }
 
 int WiFiClientSecure_light::connect(IPAddress ip, uint16_t port) {
diff --git a/tasmota/sendemail.h b/tasmota/sendemail.h
index d95ba9311..7b168b498 100644
--- a/tasmota/sendemail.h
+++ b/tasmota/sendemail.h
@@ -25,12 +25,8 @@ class SendEmail
     const bool ssl;
     const int auth_used;
 #ifdef ESP8266
-#if defined(ARDUINO_ESP8266_RELEASE_2_3_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_2)
-    WiFiClient* client;
-#else
     // use bear ssl
     BearSSL::WiFiClientSecure_light *client;
-#endif
 #else
     WiFiClient *client;
 #endif
diff --git a/tasmota/settings.ino b/tasmota/settings.ino
index 1d7ab6d04..39b1249ad 100644
--- a/tasmota/settings.ino
+++ b/tasmota/settings.ino
@@ -159,14 +159,6 @@ extern "C" {
 
 #ifdef ESP8266
 
-#if defined(ARDUINO_ESP8266_RELEASE_2_3_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_1) || defined(ARDUINO_ESP8266_RELEASE_2_4_2) || defined(ARDUINO_ESP8266_RELEASE_2_5_0) || defined(ARDUINO_ESP8266_RELEASE_2_5_1) || defined(ARDUINO_ESP8266_RELEASE_2_5_2)
-
-extern "C" uint32_t _SPIFFS_end;
-// From libraries/EEPROM/EEPROM.cpp EEPROMClass
-const uint32_t SPIFFS_END = ((uint32_t)&_SPIFFS_end - 0x40200000) / SPI_FLASH_SEC_SIZE;
-
-#else  // Core > 2.5.2 and STAGE
-
 #if AUTOFLASHSIZE
 
 #include "flash_hal.h"
@@ -187,8 +179,6 @@ const uint32_t SPIFFS_END = ((uint32_t)&_FS_end - 0x40200000) / SPI_FLASH_SEC_SI
 // Version 4.2 config = eeprom area
 const uint32_t SETTINGS_LOCATION = SPIFFS_END;  // No need for SPIFFS as it uses EEPROM area
 
-#endif  // ESP8266
-
 // Version 5.2 allow for more flash space
 const uint8_t CFG_ROTATES = 8;          // Number of flash sectors used (handles uploads)
 
@@ -632,11 +622,7 @@ void EspErase(uint32_t start_sector, uint32_t end_sector)
 //    bool result = EsptoolEraseSector(sector);    // Esptool - erases flash completely (slow)
 
     if (serial_output) {
-#ifdef ARDUINO_ESP8266_RELEASE_2_3_0
-      Serial.printf(D_LOG_APPLICATION D_ERASED_SECTOR " %d %s\n", sector, (result) ? D_OK : D_ERROR);
-#else
       Serial.printf_P(PSTR(D_LOG_APPLICATION D_ERASED_SECTOR " %d %s\n"), sector, (result) ? D_OK : D_ERROR);
-#endif
       delay(10);
     } else {
       yield();
diff --git a/tasmota/support.ino b/tasmota/support.ino
index 1d05ae2d1..50cc4f920 100644
--- a/tasmota/support.ino
+++ b/tasmota/support.ino
@@ -1080,12 +1080,8 @@ int ResponseJsonEndEnd(void)
  * GPIO Module and Template management
 \*********************************************************************************************/
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0  // Fix core 2.5.x ISR not in IRAM Exception
-uint32_t Pin(uint32_t gpio, uint32_t index) ICACHE_RAM_ATTR;
-#endif
-
-uint32_t Pin(uint32_t gpio, uint32_t index = 0);
-uint32_t Pin(uint32_t gpio, uint32_t index) {
+uint32_t ICACHE_RAM_ATTR Pin(uint32_t gpio, uint32_t index = 0);
+uint32_t ICACHE_RAM_ATTR Pin(uint32_t gpio, uint32_t index) {
 #ifdef ESP8266
   uint16_t real_gpio = gpio + index;
 #else  // ESP32
diff --git a/tasmota/support_flash_log.ino b/tasmota/support_flash_log.ino
index 5f73c4078..5055e5f21 100644
--- a/tasmota/support_flash_log.ino
+++ b/tasmota/support_flash_log.ino
@@ -112,11 +112,7 @@ DEBUG_SENSOR_LOG(PSTR("FLOG: init ..."));
 size = ESP.getSketchSize();
 // round one sector up
 start = (size + FLASH_SECTOR_SIZE - 1) & (~(FLASH_SECTOR_SIZE - 1));
-#if defined(ARDUINO_ESP8266_RELEASE_2_3_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_1) || defined(ARDUINO_ESP8266_RELEASE_2_4_2) || defined(ARDUINO_ESP8266_RELEASE_2_5_0) || defined(ARDUINO_ESP8266_RELEASE_2_5_1) || defined(ARDUINO_ESP8266_RELEASE_2_5_2)
-end = (uint32_t)&_SPIFFS_start - 0x40200000;
-#else  // Core > 2.5.2 and STAGE
 end = (uint32_t)&_FS_start - 0x40200000;
-#endif
 num_sectors = (end - start)/FLASH_SECTOR_SIZE;
 DEBUG_SENSOR_LOG(PSTR("FLOG: size: 0x%lx, start: 0x%lx, end: 0x%lx, num_sectors(dec): %lu"), size, start, end, num_sectors );
 _findFirstErasedSector();
diff --git a/tasmota/support_float.ino b/tasmota/support_float.ino
index a72712632..b99b95cd2 100644
--- a/tasmota/support_float.ino
+++ b/tasmota/support_float.ino
@@ -17,9 +17,6 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-//#ifdef ARDUINO_ESP8266_RELEASE_2_3_0
-// Functions not available in 2.3.0
-
 float fmodf(float x, float y)
 {
   // https://github.com/micropython/micropython/blob/master/lib/libm/fmodf.c
@@ -83,7 +80,6 @@ float fmodf(float x, float y)
   ux.i = uxi;
   return ux.f;
 }
-//#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
 
 double FastPrecisePow(double a, double b)
 {
diff --git a/tasmota/support_legacy_cores.ino b/tasmota/support_legacy_cores.ino
index 46546ff1d..e9a78e5ee 100644
--- a/tasmota/support_legacy_cores.ino
+++ b/tasmota/support_legacy_cores.ino
@@ -17,147 +17,6 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifdef ARDUINO_ESP8266_RELEASE_2_3_0
-/*********************************************************************************************\
- * Functions not available in core 2.3.0
-\*********************************************************************************************/
-
-// http://clc-wiki.net/wiki/C_standard_library:string.h:memchr
-void* memchr(const void* ptr, int value, size_t num)
-{
-  unsigned char *p = (unsigned char*)ptr;
-  while (num--) {
-    if (*p != (unsigned char)value) {
-      p++;
-    } else {
-      return p;
-    }
-  }
-  return 0;
-}
-
-// http://clc-wiki.net/wiki/C_standard_library:string.h:strcspn
-// Get span until any character in string
-size_t strcspn(const char *str1, const char *str2)
-{
-  size_t ret = 0;
-  while (*str1) {
-    if (strchr(str2, *str1)) {  // Slow
-      return ret;
-    } else {
-      str1++;
-      ret++;
-    }
-  }
-  return ret;
-}
-
-// https://clc-wiki.net/wiki/C_standard_library:string.h:strpbrk
-// Locate the first occurrence in the string pointed to by s1 of any character from the string pointed to by s2
-char* strpbrk(const char *s1, const char *s2)
-{
-  while(*s1) {
-    if (strchr(s2, *s1++)) {
-      return (char*)--s1;
-    }
-  }
-  return 0;
-}
-
-// https://opensource.apple.com/source/Libc/Libc-583/stdlib/FreeBSD/strtoull.c
-// Convert a string to an unsigned long long integer
-#ifndef __LONG_LONG_MAX__
-#define __LONG_LONG_MAX__ 9223372036854775807LL
-#endif
-#ifndef ULLONG_MAX
-#define ULLONG_MAX (__LONG_LONG_MAX__ * 2ULL + 1)
-#endif
-
-unsigned long long strtoull(const char *__restrict nptr, char **__restrict endptr, int base)
-{
-  const char *s = nptr;
-  char c;
-  do { c = *s++; } while (isspace((unsigned char)c));                         // Trim leading spaces
-
-  int neg = 0;
-  if (c == '-') {                                                             // Set minus flag and/or skip sign
-    neg = 1;
-    c = *s++;
-  } else {
-    if (c == '+') {
-      c = *s++;
-    }
-  }
-
-  if ((base == 0 || base == 16) && (c == '0') && (*s == 'x' || *s == 'X')) {  // Set Hexadecimal
-    c = s[1];
-    s += 2;
-    base = 16;
-  }
-  if (base == 0) { base = (c == '0') ? 8 : 10; }                              // Set Octal or Decimal
-
-  unsigned long long acc = 0;
-  int any = 0;
-  if (base > 1 && base < 37) {
-    unsigned long long cutoff = ULLONG_MAX / base;
-    int cutlim = ULLONG_MAX % base;
-    for ( ; ; c = *s++) {
-      if (c >= '0' && c <= '9')
-        c -= '0';
-      else if (c >= 'A' && c <= 'Z')
-        c -= 'A' - 10;
-      else if (c >= 'a' && c <= 'z')
-        c -= 'a' - 10;
-      else
-        break;
-
-      if (c >= base)
-        break;
-
-      if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
-        any = -1;
-      else {
-        any = 1;
-        acc *= base;
-        acc += c;
-      }
-    }
-    if (any < 0) {
-      acc = ULLONG_MAX;                                                       // Range error
-    }
-    else if (any && neg) {
-      acc = -acc;
-    }
-  }
-
-  if (endptr != nullptr) { *endptr = (char *)(any ? s - 1 : nptr); }
-
-  return acc;
-}
-
-#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
-
-
-
-#if defined(ARDUINO_ESP8266_RELEASE_2_3_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_1) || defined(ARDUINO_ESP8266_RELEASE_2_4_2) || defined(ARDUINO_ESP8266_RELEASE_2_5_0) || defined(ARDUINO_ESP8266_RELEASE_2_5_1) || defined(ARDUINO_ESP8266_RELEASE_2_5_2)
-/*********************************************************************************************\
- * Functions not available in core before 2.6.0
-\*********************************************************************************************/
-
-// https://github.com/arendst/Tasmota/issues/6856#issuecomment-554258914
-void* memmove_P(void *dest, const void *src, size_t n)
-{
-  if (src > (void*)0x40000000) {
-    return memcpy_P(dest, src, n);
-  } else {
-    return memmove(dest, src, n);
-  }
-}
-
-#endif  // ARDUINO_ESP8266_RELEASE < 2_6_0
-
-
-
 /*********************************************************************************************\
  * Core overrides
 \*********************************************************************************************/
diff --git a/tasmota/support_tasmota.ino b/tasmota/support_tasmota.ino
index 70d7f66af..0fbcbb615 100644
--- a/tasmota/support_tasmota.ino
+++ b/tasmota/support_tasmota.ino
@@ -852,11 +852,8 @@ void PerformEverySecond(void)
     }
   }
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0
   // Wifi keep alive to send Gratuitous ARP
   wifiKeepAlive();
-#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
-
 
 #ifdef ESP32
   if (11 == uptime) {      // Perform one-time ESP32 houskeeping
@@ -1027,13 +1024,8 @@ void Every250mSeconds(void)
           }
 #endif  // FIRMWARE_MINIMAL
           AddLog_P2(LOG_LEVEL_DEBUG, PSTR(D_LOG_UPLOAD "%s"), mqtt_data);
-#if defined(ARDUINO_ESP8266_RELEASE_2_3_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_1) || defined(ARDUINO_ESP8266_RELEASE_2_4_2)
-          ota_result = (HTTP_UPDATE_FAILED != ESPhttpUpdate.update(mqtt_data));
-#else
-          // If using core stage or 2.5.0+ the syntax has changed
           WiFiClient OTAclient;
           ota_result = (HTTP_UPDATE_FAILED != ESPhttpUpdate.update(OTAclient, mqtt_data));
-#endif
           if (!ota_result) {
 #ifndef FIRMWARE_MINIMAL
             int ota_error = ESPhttpUpdate.getLastError();
diff --git a/tasmota/support_wifi.ino b/tasmota/support_wifi.ino
index 75de2523f..3274cfc4b 100644
--- a/tasmota/support_wifi.ino
+++ b/tasmota/support_wifi.ino
@@ -153,14 +153,11 @@ void WiFiSetSleepMode(void)
  */
 
 // Sleep explanation: https://github.com/esp8266/Arduino/blob/3f0c601cfe81439ce17e9bd5d28994a7ed144482/libraries/ESP8266WiFi/src/ESP8266WiFiGeneric.cpp#L255
-#if defined(ARDUINO_ESP8266_RELEASE_2_4_1) || defined(ARDUINO_ESP8266_RELEASE_2_4_2)
-#else  // Enabled in 2.3.0, 2.4.0 and stage
   if (ssleep && Settings.flag3.sleep_normal) {  // SetOption60 - Enable normal sleep instead of dynamic sleep
     WiFi.setSleepMode(WIFI_LIGHT_SLEEP);        // Allow light sleep during idle times
   } else {
     WiFi.setSleepMode(WIFI_MODEM_SLEEP);        // Disable sleep (Esp8288/Arduino core and sdk default)
   }
-#endif
   WifiSetOutputPower();
 }
 
@@ -172,12 +169,6 @@ void WifiBegin(uint8_t flag, uint8_t channel)
   UdpDisconnect();
 #endif  // USE_EMULATION
 
-#ifdef ARDUINO_ESP8266_RELEASE_2_3_0  // (!strncmp_P(ESP.getSdkVersion(),PSTR("1.5.3"),5))
-  AddLog_P(LOG_LEVEL_DEBUG, S_LOG_WIFI, PSTR(D_PATCH_ISSUE_2186));
-//  WiFi.mode(WIFI_OFF);      // See https://github.com/esp8266/Arduino/issues/2186
-  WifiSetMode(WIFI_OFF);
-#endif
-
   WiFi.persistent(false);   // Solve possible wifi init errors (re-add at 6.2.1.16 #4044, #4083)
   WiFi.disconnect(true);    // Delete SDK wifi config
   delay(200);
@@ -652,7 +643,6 @@ void EspRestart(void)
   ESP_Restart();
 }
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0
 //
 // Gratuitous ARP, backported from https://github.com/esp8266/Arduino/pull/6889
 //
@@ -700,4 +690,3 @@ void wifiKeepAlive(void) {
     SetNextTimeInterval(wifiTimer, wifiTimerSec * 1000);
   }
 }
-#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
diff --git a/tasmota/tasmota.ino b/tasmota/tasmota.ino
index 1da4e7606..43e019e33 100644
--- a/tasmota/tasmota.ino
+++ b/tasmota/tasmota.ino
@@ -34,7 +34,7 @@
 \*********************************************************************************************/
 
 // Location specific includes
-#include <core_version.h>                   // Arduino_Esp8266 version information (ARDUINO_ESP8266_RELEASE and ARDUINO_ESP8266_RELEASE_2_3_0)
+#include <core_version.h>                   // Arduino_Esp8266 version information (ARDUINO_ESP8266_RELEASE and ARDUINO_ESP8266_RELEASE_2_7_1)
 #include "tasmota_compat.h"
 #include "tasmota_version.h"                // Tasmota version information
 #include "tasmota.h"                        // Enumeration used in my_user_config.h
@@ -46,13 +46,6 @@
 #include "i18n.h"                           // Language support configured by my_user_config.h
 #include "tasmota_template.h"               // Hardware configuration
 
-#ifdef ARDUINO_ESP8266_RELEASE_2_4_0
-#include "lwip/init.h"
-#if LWIP_VERSION_MAJOR != 1
-  #error Please use stable lwIP v1.4
-#endif
-#endif
-
 // Libraries
 #include <ESP8266HTTPClient.h>              // Ota
 #include <ESP8266httpUpdate.h>              // Ota
diff --git a/tasmota/tasmota_configurations.h b/tasmota/tasmota_configurations.h
index 58d08d543..ad9d64d08 100644
--- a/tasmota/tasmota_configurations.h
+++ b/tasmota/tasmota_configurations.h
@@ -280,13 +280,11 @@
 
 #define USE_SPI                                  // Hardware SPI using GPIO12(MISO), GPIO13(MOSI) and GPIO14(CLK) in addition to two user selectable GPIOs(CS and DC)
     #define USE_DISPLAY_ILI9341                  // [DisplayModel 4] Enable ILI9341 Tft 480x320 display (+19k code)
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0            // There is not enough spare RAM with core 2.3.0 to support the following
     #define USE_DISPLAY_EPAPER_29                // [DisplayModel 5] Enable e-paper 2.9 inch display (+19k code)
     #define USE_DISPLAY_EPAPER_42                // [DisplayModel 6] Enable e-paper 4.2 inch display
 //    #define USE_DISPLAY_ILI9488                  // [DisplayModel 8]
 //    #define USE_DISPLAY_SSD1351                  // [DisplayModel 9]
 //    #define USE_DISPLAY_RA8876                   // [DisplayModel 10]
-#endif
 
 #undef DEBUG_THEO                                // Disable debug code
 #undef USE_DEBUG_DRIVER                          // Disable debug code
diff --git a/tasmota/tasmota_globals.h b/tasmota/tasmota_globals.h
index 42e63f206..e4312d0b3 100644
--- a/tasmota/tasmota_globals.h
+++ b/tasmota/tasmota_globals.h
@@ -128,8 +128,8 @@ String EthernetMacAddress(void);
   const uint16_t WEB_LOG_SIZE = 4000;          // Max number of characters in weblog
 #endif
 
-#if defined(USE_TLS) && defined(ARDUINO_ESP8266_RELEASE_2_3_0)
-  #error "TLS is no more supported on Core 2.3.0, use 2.4.2 or higher."
+#if defined(ARDUINO_ESP8266_RELEASE_2_3_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_1) || defined(ARDUINO_ESP8266_RELEASE_2_4_2) || defined(ARDUINO_ESP8266_RELEASE_2_5_0) || defined(ARDUINO_ESP8266_RELEASE_2_5_1) || defined(ARDUINO_ESP8266_RELEASE_2_5_2)
+  #error "Arduino ESP8266 Core versions before 2.7.1 are not supported"
 #endif
 
 #ifndef MQTT_MAX_PACKET_SIZE
diff --git a/tasmota/xdrv_01_webserver.ino b/tasmota/xdrv_01_webserver.ino
index 8ba98f91e..e42b17db4 100644
--- a/tasmota/xdrv_01_webserver.ino
+++ b/tasmota/xdrv_01_webserver.ino
@@ -913,14 +913,8 @@ void WifiManagerBegin(bool reset_only)
   int channel = WIFI_SOFT_AP_CHANNEL;
   if ((channel < 1) || (channel > 13)) { channel = 1; }
 
-#ifdef ARDUINO_ESP8266_RELEASE_2_3_0
-  // bool softAP(const char* ssid, const char* passphrase = NULL, int channel = 1, int ssid_hidden = 0);
-  WiFi.softAP(my_hostname, WIFI_AP_PASSPHRASE, channel, 0);
-#else
   // bool softAP(const char* ssid, const char* passphrase = NULL, int channel = 1, int ssid_hidden = 0, int max_connection = 4);
   WiFi.softAP(my_hostname, WIFI_AP_PASSPHRASE, channel, 0, 1);
-#endif
-
   delay(500); // Without delay I've seen the IP address blank
   /* Setup the DNS server redirecting all the domains to the apIP */
   DnsServer->setErrorReplyCode(DNSReplyCode::NoError);
@@ -992,10 +986,6 @@ void WSContentBegin(int code, int ctype)
 {
   Webserver->client().flush();
   WSHeaderSend();
-#ifdef ARDUINO_ESP8266_RELEASE_2_3_0
-  Webserver->sendHeader(F("Accept-Ranges"),F("none"));
-  Webserver->sendHeader(F("Transfer-Encoding"),F("chunked"));
-#endif
   Webserver->setContentLength(CONTENT_LENGTH_UNKNOWN);
   WSSend(code, ctype, "");                        // Signal start of chunked content
   Web.chunk_buffer = "";
@@ -1004,15 +994,7 @@ void WSContentBegin(int code, int ctype)
 void _WSContentSend(const String& content)        // Low level sendContent for all core versions
 {
   size_t len = content.length();
-
-#ifdef ARDUINO_ESP8266_RELEASE_2_3_0
-  const char * footer = "\r\n";
-  char chunk_size[11];
-  sprintf(chunk_size, "%x\r\n", len);
-  Webserver->sendContent(String() + chunk_size + content + footer);
-#else
   Webserver->sendContent(content);
-#endif
 
 #ifdef USE_DEBUG_DRIVER
   ShowFreeMem(PSTR("WSContentSend"));
@@ -1377,7 +1359,7 @@ void HandleRoot(void)
           "c",               // c - Unique HTML id
           "#000", "#fff",    // Black to White
           4,                 // sl4 - Unique range HTML id - Used as source for Saturation begin color
-          Settings.flag3.slider_dimmer_stay_on, 100,  // Range 0/1 to 100%
+          Settings.flag3.slider_dimmer_stay_on, 100,  // Range 0/1 to 100% (SetOption77 - Do not power off if slider moved to far left)
           Settings.light_dimmer,
           'd', 0);           // d0 - Value id is related to lc("d0", value) and WebGetArg("d0", tmp, sizeof(tmp));
 
@@ -1389,7 +1371,7 @@ void HandleRoot(void)
             "f",             // f - Unique HTML id
             "#000", "#fff",  // Black to White
             5,               // sl5 - Unique range HTML id - Not used
-            Settings.flag3.slider_dimmer_stay_on, 100,  // Range 0/1 to 100%
+            Settings.flag3.slider_dimmer_stay_on, 100,  // Range 0/1 to 100% (SetOption77 - Do not power off if slider moved to far left)
             LightGetDimmer(2),
             'w', 0);         // w0 - Value id is related to lc("w0", value) and WebGetArg("w0", tmp, sizeof(tmp));
         }
@@ -2367,14 +2349,7 @@ void HandleBackupConfiguration(void)
     }
   }
 
-#ifdef ARDUINO_ESP8266_RELEASE_2_3_0
-  size_t written = myClient.write((const char*)settings_buffer, sizeof(Settings));
-  if (written < sizeof(Settings)) {  // https://github.com/esp8266/Arduino/issues/3218
-    myClient.write((const char*)settings_buffer +written, sizeof(Settings) -written);
-  }
-#else
   myClient.write((const char*)settings_buffer, sizeof(Settings));
-#endif
 
   SettingsBufferFree();
 
@@ -3152,14 +3127,9 @@ int WebSend(char *buffer)
 
     DEBUG_CORE_LOG(PSTR("WEB: Uri |%s|"), url.c_str());
 
-#if defined(ARDUINO_ESP8266_RELEASE_2_3_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_1) || defined(ARDUINO_ESP8266_RELEASE_2_4_2)
-    HTTPClient http;
-    if (http.begin(UrlEncode(url))) {         // UrlEncode(url) = |http://192.168.178.86/cm?cmnd=POWER1%20ON|
-#else
     WiFiClient http_client;
     HTTPClient http;
     if (http.begin(http_client, UrlEncode(url))) {  // UrlEncode(url) = |http://192.168.178.86/cm?cmnd=POWER1%20ON|
-#endif
       int http_code = http.GET();             // Start connection and send HTTP header
       if (http_code > 0) {                    // http_code will be negative on error
         if (http_code == HTTP_CODE_OK || http_code == HTTP_CODE_MOVED_PERMANENTLY) {
diff --git a/tasmota/xdrv_02_mqtt.ino b/tasmota/xdrv_02_mqtt.ino
index a24d51de3..1f232cff8 100644
--- a/tasmota/xdrv_02_mqtt.ino
+++ b/tasmota/xdrv_02_mqtt.ino
@@ -1217,11 +1217,7 @@ void CmndTlsDump(void) {
   uint32_t end   = start + tls_block_len -1;
   for (uint32_t pos = start; pos < end; pos += 0x10) {
     uint32_t* values = (uint32_t*)(pos);
-#ifdef ARDUINO_ESP8266_RELEASE_2_3_0
-    Serial.printf("%08x:  %08x %08x %08x %08x\n", pos, bswap32(values[0]), bswap32(values[1]), bswap32(values[2]), bswap32(values[3]));
-#else
     Serial.printf_P(PSTR("%08x:  %08x %08x %08x %08x\n"), pos, bswap32(values[0]), bswap32(values[1]), bswap32(values[2]), bswap32(values[3]));
-#endif
   }
 }
 #endif  // DEBUG_DUMP_TLS
diff --git a/tasmota/xdrv_10_scripter.ino b/tasmota/xdrv_10_scripter.ino
index b885feadf..922e75ebc 100755
--- a/tasmota/xdrv_10_scripter.ino
+++ b/tasmota/xdrv_10_scripter.ino
@@ -1164,11 +1164,9 @@ uint32_t pulse_ltime_hl;
 uint32_t pulse_ltime_lh;
 uint8_t pt_pin;
 
-void MP_Timer(void) ICACHE_RAM_ATTR;
-
 #define MPT_DEBOUNCE 10
 
-void MP_Timer(void) {
+void ICACHE_RAM_ATTR MP_Timer(void) {
   uint32_t level = digitalRead(pt_pin&0x3f);
   uint32_t ms = millis();
   uint32_t time;
@@ -2899,19 +2897,6 @@ char *getop(char *lp, uint8_t *operand) {
 
 
 #ifdef ESP8266
-#if defined(ARDUINO_ESP8266_RELEASE_2_3_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_1)
-// All version before core 2.4.2
-// https://github.com/esp8266/Arduino/issues/2557
-extern "C" {
-#include <cont.h>
-  extern cont_t g_cont;
-}
-uint16_t GetStack(void) {
-  register uint32_t *sp asm("a1");
-  return (4 * (sp - g_cont.stack));
-}
-
-#else
 extern "C" {
 #include <cont.h>
   extern cont_t* g_pcont;
@@ -2920,7 +2905,6 @@ uint16_t GetStack(void) {
   register uint32_t *sp asm("a1");
   return (4 * (sp - g_pcont->stack));
 }
-#endif
 #else
 uint16_t GetStack(void) {
   register uint8_t *sp asm("a1");
@@ -4349,18 +4333,10 @@ uint8_t reject(char *name) {
   if (*name=='_') return 1;
   if (*name=='.') return 1;
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0
   if (!strncasecmp(name,"SPOTLI~1",REJCMPL)) return 1;
   if (!strncasecmp(name,"TRASHE~1",REJCMPL)) return 1;
   if (!strncasecmp(name,"FSEVEN~1",REJCMPL)) return 1;
   if (!strncasecmp(name,"SYSTEM~1",REJCMPL)) return 1;
-#else
-  if (!strcasecmp(name,"SPOTLI~1")) return 1;
-  if (!strcasecmp(name,"TRASHE~1")) return 1;
-  if (!strcasecmp(name,"FSEVEN~1")) return 1;
-  if (!strcasecmp(name,"SYSTEM~1")) return 1;
-#endif
-
   if (!strncasecmp(name,"System Volume",13)) return 1;
   return 0;
 }
diff --git a/tasmota/xdrv_26_ariluxrf.ino b/tasmota/xdrv_26_ariluxrf.ino
index 5027dfdcb..b0f20e8a6 100644
--- a/tasmota/xdrv_26_ariluxrf.ino
+++ b/tasmota/xdrv_26_ariluxrf.ino
@@ -45,11 +45,9 @@ struct ARILUX {
   uint8_t rf_toggle = 0;
 } Arilux;
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0          // Fix core 2.5.x ISR not in IRAM Exception
 #ifndef USE_WS2812_DMA                         // Collides with Neopixelbus but solves RF misses
 void AriluxRfInterrupt(void) ICACHE_RAM_ATTR;  // As iram is tight and it works this way too
 #endif  // USE_WS2812_DMA
-#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
 
 void AriluxRfInterrupt(void)
 {
diff --git a/tasmota/xdrv_99_debug.ino b/tasmota/xdrv_99_debug.ino
index 08f451c30..7471d3095 100644
--- a/tasmota/xdrv_99_debug.ino
+++ b/tasmota/xdrv_99_debug.ino
@@ -189,24 +189,6 @@ void CpuLoadLoop(void)
 /*******************************************************************************************/
 
 #ifdef ESP8266
-#if defined(ARDUINO_ESP8266_RELEASE_2_3_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_0) || defined(ARDUINO_ESP8266_RELEASE_2_4_1)
-// All version before core 2.4.2
-// https://github.com/esp8266/Arduino/issues/2557
-
-extern "C" {
-#include <cont.h>
-  extern cont_t g_cont;
-}
-
-void DebugFreeMem(void)
-{
-  register uint32_t *sp asm("a1");
-
-//  AddLog_P2(LOG_LEVEL_DEBUG, PSTR(D_LOG_DEBUG "FreeRam %d, FreeStack %d, UnmodifiedStack %d (%s)"), ESP.getFreeHeap(), 4 * (sp - g_cont.stack), cont_get_free_stack(&g_cont), XdrvMailbox.data);
-  AddLog_P2(LOG_LEVEL_DEBUG, PSTR(D_LOG_DEBUG "FreeRam %d, FreeStack %d (%s)"), ESP.getFreeHeap(), 4 * (sp - g_cont.stack), XdrvMailbox.data);
-}
-
-#else
 // All version from core 2.4.2
 // https://github.com/esp8266/Arduino/pull/5018
 // https://github.com/esp8266/Arduino/pull/4553
@@ -223,8 +205,6 @@ void DebugFreeMem(void)
   AddLog_P2(LOG_LEVEL_DEBUG, PSTR(D_LOG_DEBUG "FreeRam %d, FreeStack %d (%s)"), ESP.getFreeHeap(), 4 * (sp - g_pcont->stack), XdrvMailbox.data);
 }
 
-#endif  // ARDUINO_ESP8266_RELEASE_2_x_x
-
 #else  // ESP32
 
 void DebugFreeMem(void)
diff --git a/tasmota/xsns_01_counter.ino b/tasmota/xsns_01_counter.ino
index ae03ef324..48452752f 100644
--- a/tasmota/xsns_01_counter.ino
+++ b/tasmota/xsns_01_counter.ino
@@ -47,15 +47,7 @@ struct COUNTER {
 uint32_t last_cycle;
 uint32_t cycle_time;
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0  // Fix core 2.5.x ISR not in IRAM Exception
-void CounterUpdate(uint8_t index) ICACHE_RAM_ATTR;
-void CounterUpdate1(void) ICACHE_RAM_ATTR;
-void CounterUpdate2(void) ICACHE_RAM_ATTR;
-void CounterUpdate3(void) ICACHE_RAM_ATTR;
-void CounterUpdate4(void) ICACHE_RAM_ATTR;
-#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
-
-void CounterUpdate(uint8_t index)
+void ICACHE_RAM_ATTR CounterUpdate(uint8_t index)
 {
   uint32_t time = micros();
   uint32_t debounce_time;
@@ -125,22 +117,22 @@ void CounterUpdate(uint8_t index)
   }
 }
 
-void CounterUpdate1(void)
+void ICACHE_RAM_ATTR CounterUpdate1(void)
 {
   CounterUpdate(0);
 }
 
-void CounterUpdate2(void)
+void ICACHE_RAM_ATTR CounterUpdate2(void)
 {
   CounterUpdate(1);
 }
 
-void CounterUpdate3(void)
+void ICACHE_RAM_ATTR CounterUpdate3(void)
 {
   CounterUpdate(2);
 }
 
-void CounterUpdate4(void)
+void ICACHE_RAM_ATTR CounterUpdate4(void)
 {
   CounterUpdate(3);
 }
diff --git a/tasmota/xsns_35_tx20.ino b/tasmota/xsns_35_tx20.ino
index cf41a41fb..3ab33e402 100644
--- a/tasmota/xsns_35_tx20.ino
+++ b/tasmota/xsns_35_tx20.ino
@@ -150,11 +150,7 @@ uint32_t tx2x_last_available = 0;
 uint32_t tx23_stage = 0;
 #endif  // USE_TX23_WIND_SENSOR
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0      // Fix core 2.5.x ISR not in IRAM Exception
-void TX2xStartRead(void) ICACHE_RAM_ATTR;  // As iram is tight and it works this way too
-#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
-
-void TX2xStartRead(void)
+void ICACHE_RAM_ATTR TX2xStartRead(void)
 {
   /**
    * La Crosse TX20 Anemometer datagram every 2 seconds
diff --git a/tasmota/xsns_53_sml.ino b/tasmota/xsns_53_sml.ino
index a75a8fbd8..66981d2ba 100755
--- a/tasmota/xsns_53_sml.ino
+++ b/tasmota/xsns_53_sml.ino
@@ -1811,16 +1811,7 @@ struct SML_COUNTER {
 #endif
 } sml_counters[MAX_COUNTERS];
 
-
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0       // Fix core 2.5.x ISR not in IRAM Exception
-void SML_CounterUpd(uint8_t index) ICACHE_RAM_ATTR;
-void SML_CounterUpd1(void) ICACHE_RAM_ATTR;
-void SML_CounterUpd2(void) ICACHE_RAM_ATTR;
-void SML_CounterUpd3(void) ICACHE_RAM_ATTR;
-void SML_CounterUpd4(void) ICACHE_RAM_ATTR;
-#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
-
-void SML_CounterUpd(uint8_t index) {
+void ICACHE_RAM_ATTR SML_CounterUpd(uint8_t index) {
 
   uint8_t level=digitalRead(meter_desc_p[sml_counters[index].sml_cnt_old_state].srcpin);
   if (!level) {
@@ -1838,19 +1829,19 @@ void SML_CounterUpd(uint8_t index) {
   }
 }
 
-void SML_CounterUpd1(void) {
+void ICACHE_RAM_ATTR SML_CounterUpd1(void) {
   SML_CounterUpd(0);
 }
 
-void SML_CounterUpd2(void) {
+void ICACHE_RAM_ATTR SML_CounterUpd2(void) {
   SML_CounterUpd(1);
 }
 
-void SML_CounterUpd3(void) {
+void ICACHE_RAM_ATTR SML_CounterUpd3(void) {
   SML_CounterUpd(2);
 }
 
-void SML_CounterUpd4(void) {
+void ICACHE_RAM_ATTR SML_CounterUpd4(void) {
   SML_CounterUpd(3);
 }
 
diff --git a/tasmota/xsns_68_windmeter.ino b/tasmota/xsns_68_windmeter.ino
index 5487c898c..677cfc8b3 100644
--- a/tasmota/xsns_68_windmeter.ino
+++ b/tasmota/xsns_68_windmeter.ino
@@ -72,11 +72,7 @@ struct WINDMETER {
 #endif  // USE_WINDMETER_NOSTATISTICS
 } WindMeter;
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0  // Fix core 2.5.x ISR not in IRAM Exception
-void WindMeterUpdateSpeed(void) ICACHE_RAM_ATTR;
-#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
-
-void WindMeterUpdateSpeed(void)
+void ICACHE_RAM_ATTR WindMeterUpdateSpeed(void)
 {
   uint32_t time = micros();
   uint32_t time_diff = time - WindMeter.counter_time;
diff --git a/tasmota/xsns_74_lmt01.ino b/tasmota/xsns_74_lmt01.ino
index d52e6dae2..522b82281 100644
--- a/tasmota/xsns_74_lmt01.ino
+++ b/tasmota/xsns_74_lmt01.ino
@@ -40,13 +40,9 @@ void LMT01_Init(void) {
   }
 }
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0  // Fix core 2.5.x ISR not in IRAM Exception
-void LMT01_countPulse(void) ICACHE_RAM_ATTR;
-#endif // ARDUINO_ESP8266_RELEASE_2_3_0
-
 volatile int lmt01_pulseCount = 0;
 
-void LMT01_countPulse(void) {
+void ICACHE_RAM_ATTR LMT01_countPulse(void) {
   lmt01_pulseCount++;
 }
 
@@ -81,7 +77,7 @@ int LMT01_getPulses(void) {
     hold = lmt01_pulseCount;
     delay(1);
   }
-  // discard spurious low counts 
+  // discard spurious low counts
   if (timeout > 0 && hold >= 10) {
     return hold;
   }