diff --git a/boards.txt b/boards.txt
index 9499d23547..3d2c355c29 100644
--- a/boards.txt
+++ b/boards.txt
@@ -4960,7 +4960,7 @@ espinotee.menu.baud.3000000.upload.speed=3000000
 wifinfo.name=WifInfo
 wifinfo.build.board=WIFINFO
 wifinfo.build.variant=wifinfo
-wifinfo.menu.ESPModule.ESP07192=ESP07 (1M/192K SPIFFS)
+wifinfo.menu.ESPModule.ESP07192=ESP07 (1M/192K FS)
 wifinfo.menu.ESPModule.ESP07192.build.board=ESP8266_ESP07
 wifinfo.menu.ESPModule.ESP07192.build.flash_ld=eagle.flash.1m192.ld
 wifinfo.menu.ESPModule.ESP07192.build.flash_size=1M
@@ -4968,7 +4968,7 @@ wifinfo.menu.ESPModule.ESP07192.build.spiffs_blocksize=4096
 wifinfo.menu.ESPModule.ESP07192.build.spiffs_end=0xFB000
 wifinfo.menu.ESPModule.ESP07192.build.spiffs_start=0xCB000
 wifinfo.menu.ESPModule.ESP07192.upload.maximum_size=827376
-wifinfo.menu.ESPModule.ESP12=ESP12 (4M/1M SPIFFS)
+wifinfo.menu.ESPModule.ESP12=ESP12 (4M/1M FS)
 wifinfo.menu.ESPModule.ESP12.build.board=ESP8266_ESP12
 wifinfo.menu.ESPModule.ESP12.build.flash_ld=eagle.flash.4m1m.ld
 wifinfo.menu.ESPModule.ESP12.build.flash_size=4M
diff --git a/cores/esp8266/FS.h b/cores/esp8266/FS.h
index aa47527812..93ef68ed5a 100644
--- a/cores/esp8266/FS.h
+++ b/cores/esp8266/FS.h
@@ -266,7 +266,7 @@ using fs::SPIFFSConfig;
 #endif //FS_NO_GLOBALS
 
 #if !defined(NO_GLOBAL_INSTANCES) && !defined(NO_GLOBAL_SPIFFS)
-extern fs::FS SPIFFS;
+extern fs::FS SPIFFS __attribute__((deprecated("SPIFFS has been deprecated. Please consider moving to LittleFS or other filesystems.")));
 #endif
 
 #endif //FS_H
diff --git a/cores/esp8266/spiffs_api.cpp b/cores/esp8266/spiffs_api.cpp
index 1f0278bfc5..df3e44245d 100644
--- a/cores/esp8266/spiffs_api.cpp
+++ b/cores/esp8266/spiffs_api.cpp
@@ -37,8 +37,8 @@ int32_t spiffs_hal_read(uint32_t addr, uint32_t size, uint8_t *dst) {
     return flash_hal_read(addr, size, dst);
 }
 
-
-
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 
 namespace spiffs_impl {
 
@@ -149,6 +149,8 @@ extern "C" void spiffs_request_end(void)
     SPIFFS.end();
 }
 
+#pragma GCC diagnostic pop
+
 #endif // ARDUINO
 #endif // !CORE_MOCK
 
diff --git a/cores/esp8266/spiffs_api.h b/cores/esp8266/spiffs_api.h
index a40d59b0a8..1ea04849e1 100644
--- a/cores/esp8266/spiffs_api.h
+++ b/cores/esp8266/spiffs_api.h
@@ -171,7 +171,7 @@ class SPIFFSImpl : public FSImpl
             return false;
         }
         _cfg = *static_cast<const SPIFFSConfig *>(&cfg);
-	return true;
+        return true;
     }
 
     bool begin() override
diff --git a/doc/boards.rst b/doc/boards.rst
index a27c1d5cfb..7ab98e2513 100644
--- a/doc/boards.rst
+++ b/doc/boards.rst
@@ -344,7 +344,7 @@ Parameters in Arduino IDE:
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 - Card: "WEMOS D1 Mini Lite"
-- Flash Size: "1M (512K SPIFFS)"
+- Flash Size: "1M (512K FS)"
 - CPU Frequency: "80 Mhz"
 
 Power:
diff --git a/doc/esp8266wifi/bearssl-client-secure-class.rst b/doc/esp8266wifi/bearssl-client-secure-class.rst
index dc6886342a..b145e68a05 100644
--- a/doc/esp8266wifi/bearssl-client-secure-class.rst
+++ b/doc/esp8266wifi/bearssl-client-secure-class.rst
@@ -102,9 +102,9 @@ The web browser you're using to read this document keeps a list of 100s of certi
 
 In many cases your application will know the specific CA it needs to validate web or MQTT servers against (often just a single, self-signing CA private to your institution).  Simply load your private CA in a `BearSSL::X509List` and use that as your trust anchor.
 
-However, there are cases where you will not know beforehand which CA you will need (i.e. a user enters a website through a keypad), and you need to keep the list of CAs just like your web browser.  In those cases, you need to generate a certificate bundle on the PC while compiling your application, upload the `certs.ar` bundle to SPIFFS or SD when uploading your application binary, and pass it to a `BearSSL::CertStore()` in order to validate TLS peers.
+However, there are cases where you will not know beforehand which CA you will need (i.e. a user enters a website through a keypad), and you need to keep the list of CAs just like your web browser.  In those cases, you need to generate a certificate bundle on the PC while compiling your application, upload the `certs.ar` bundle to LittleFS or SD when uploading your application binary, and pass it to a `BearSSL::CertStore()` in order to validate TLS peers.
 
-See the `BearSSL_CertStore` example for full details as the `BearSSL::CertStore` requires the creation of a cookie-cutter object for filesystem access (because the SD and SPIFFS filesystems are presently incompatible with each other).  At a high level in your `setup()` you will call `BearSSL::initCertStore()` on a global object, and then pass this global certificate store to `client.setCertStore(&gCA)` before every connection attempt to enable it as a validation option.
+See the `BearSSL_CertStore` example for full details.
 
 Supported Crypto
 ~~~~~~~~~~~~~~~~
diff --git a/doc/esp8266wifi/client-secure-class.rst b/doc/esp8266wifi/client-secure-class.rst
index 22501da4a8..597a198cc7 100644
--- a/doc/esp8266wifi/client-secure-class.rst
+++ b/doc/esp8266wifi/client-secure-class.rst
@@ -42,23 +42,24 @@ Load client certificate from file system.
 .. code:: cpp
 
     #include <FS.h>
+    #include <LittleFS.h>
     #include <ESP8266WiFi.h>
     #include <WiFiClientSecure.h>
 
-    const char* certyficateFile = "/client.cer";
+    const char* certificateFile = "/client.cer";
 
 *setup() or loop()*
 
 .. code:: cpp
 
-    if (!SPIFFS.begin()) 
+    if (!LittleFS.begin())
     {
       Serial.println("Failed to mount the file system");
       return;
     }
 
-    Serial.printf("Opening %s", certyficateFile);
-    File crtFile = SPIFFS.open(certyficateFile, "r");
+    Serial.printf("Opening %s", certificateFile);
+    File crtFile = LittleFS.open(certificateFile, "r");
     if (!crtFile)
     {
       Serial.println(" Failed!");
@@ -66,7 +67,7 @@ Load client certificate from file system.
 
     WiFiClientSecure client;
 
-    Serial.print("Loading %s", certyficateFile);
+    Serial.print("Loading %s", certificateFile);
     if (!client.loadCertificate(crtFile))
     {
       Serial.println(" Failed!");
diff --git a/doc/faq/readme.rst b/doc/faq/readme.rst
index ee76138dff..fda5fb6592 100644
--- a/doc/faq/readme.rst
+++ b/doc/faq/readme.rst
@@ -79,7 +79,7 @@ perform. It is not listed among libraries verified to work with ESP8266.
 
 `Read more <a03-library-does-not-work.rst>`__.
 
-In the IDE, for ESP-12E that has 4M flash, I can choose 4M (1M SPIFFS) or 4M (3M SPIFFS). No matter what I select, the IDE tells me the maximum code space is about 1M. Where does my flash go?
+In the IDE, for ESP-12E that has 4M flash, I can choose 4M (1M FS) or 4M (3M FS). No matter what I select, the IDE tells me the maximum code space is about 1M. Where does my flash go?
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 The reason we cannot have more than 1MB of code in flash has to do with
@@ -90,7 +90,7 @@ total, but switching such "banks" on the fly is not easy and efficient,
 so we don't bother doing that. Besides, no one has so far complained
 about 1MB of code space being insufficient for practical purposes.
 
-The option to choose 3M or 1M SPIFFS is to optimize the upload time.
+The option to choose 3M or 1M filesystem is to optimize the upload time.
 Uploading 3MB takes a long time so sometimes you can just use 1MB. Other
 2MB of flash can still be used with ``ESP.flashRead`` and
 ``ESP.flashWrite`` APIs if necessary.
diff --git a/doc/filesystem.rst b/doc/filesystem.rst
index abf47a7ead..57b69d3834 100644
--- a/doc/filesystem.rst
+++ b/doc/filesystem.rst
@@ -63,6 +63,16 @@ following include to the sketch:
 
     #include "FS.h"
 
+SPIFFS Deprecation Warning
+--------------------------
+
+SPIFFS is currently deprecated and may be removed in future releases of
+the core.  Please consider moving your code to LittleFS.  SPIFFS is not
+actively supported anymore by the upstream developer, while LittleFS is
+under active development, supports real directories, and is many times
+faster for most operations.
+
+
 SPIFFS and LittleFS
 -------------------
 
diff --git a/doc/installing.rst b/doc/installing.rst
index 515fc891f0..cd8e58a7ab 100644
--- a/doc/installing.rst
+++ b/doc/installing.rst
@@ -244,6 +244,6 @@ BeagleBone, CubieBoard).
 - `What is PlatformIO? <https://docs.platformio.org/en/latest/what-is-platformio.html?utm_source=arduino-esp8266>`__
 - `PlatformIO IDE <https://platformio.org/platformio-ide?utm_source=arduino-esp8266>`__
 - `PlatformIO Core <https://docs.platformio.org/en/latest/core.html?utm_source=arduino-esp8266>`__ (command line tool)
-- `Advanced usage <https://docs.platformio.org/en/latest/platforms/espressif8266.html?utm_source=arduino-esp8266>`__ - custom settings, uploading to SPIFFS, Over-the-Air (OTA), staging version
+- `Advanced usage <https://docs.platformio.org/en/latest/platforms/espressif8266.html?utm_source=arduino-esp8266>`__ - custom settings, uploading to LittleFS, Over-the-Air (OTA), staging version
 - `Integration with Cloud and Standalone IDEs <https://docs.platformio.org/en/latest/ide.html?utm_source=arduino-esp8266>`__ - Cloud9, Codeanywhere, Eclipse Che (Codenvy), Atom, CLion, Eclipse, Emacs, NetBeans, Qt Creator, Sublime Text, VIM, Visual Studio, and VSCode
 - `Project Examples <https://docs.platformio.org/en/latest/platforms/espressif8266.html?utm_source=arduino-esp8266#examples>`__
diff --git a/doc/libraries.rst b/doc/libraries.rst
index fc44d46f5a..8e8bdcb637 100644
--- a/doc/libraries.rst
+++ b/doc/libraries.rst
@@ -25,7 +25,7 @@ This is a bit different from standard EEPROM class. You need to call ``EEPROM.be
 
 ``EEPROM.write`` does not write to flash immediately, instead you must call ``EEPROM.commit()`` whenever you wish to save changes to flash. ``EEPROM.end()`` will also commit, and will release the RAM copy of EEPROM contents.
 
-EEPROM library uses one sector of flash located just after the SPIFFS.
+EEPROM library uses one sector of flash located just after the embedded filesystem.
 
 `Three examples <https://github.com/esp8266/Arduino/tree/master/libraries/EEPROM>`__  included.
 
diff --git a/doc/ota_updates/readme.rst b/doc/ota_updates/readme.rst
index a783bc782c..35eb931507 100755
--- a/doc/ota_updates/readme.rst
+++ b/doc/ota_updates/readme.rst
@@ -360,7 +360,7 @@ If this is the case, then most likely ESP module has not been reset after initia
 The most common causes of OTA failure are as follows:
 
 - not enough physical memory on the chip (e.g. ESP01 with 512K flash memory is not enough for OTA).
-- too much memory declared for SPIFFS so new sketch will not fit between existing sketch and SPIFFS – see `Update process - memory view <#update-process-memory-view>`__.
+- too much memory declared for the filesystem so new sketch will not fit between existing sketch and the filesystem – see `Update process - memory view <#update-process-memory-view>`__.
 - too little memory declared in Arduino IDE for your selected board (i.e. less than physical size).
 - not resetting the ESP module after initial upload using serial port.
 
diff --git a/libraries/DNSServer/examples/CaptivePortalAdvanced/CaptivePortalAdvanced.ino b/libraries/DNSServer/examples/CaptivePortalAdvanced/CaptivePortalAdvanced.ino
index e97dfbc0a4..5f1f5020a1 100644
--- a/libraries/DNSServer/examples/CaptivePortalAdvanced/CaptivePortalAdvanced.ino
+++ b/libraries/DNSServer/examples/CaptivePortalAdvanced/CaptivePortalAdvanced.ino
@@ -56,7 +56,7 @@ unsigned int status = WL_IDLE_STATUS;
 
 void setup() {
   delay(1000);
-  Serial.begin(9600);
+  Serial.begin(115200);
   Serial.println();
   Serial.println("Configuring access point...");
   /* You can remove the password parameter if you want the AP to be open. */
diff --git a/libraries/EEPROM/examples/eeprom_read/eeprom_read.ino b/libraries/EEPROM/examples/eeprom_read/eeprom_read.ino
index 5ffbe8240e..3295fecf9f 100644
--- a/libraries/EEPROM/examples/eeprom_read/eeprom_read.ino
+++ b/libraries/EEPROM/examples/eeprom_read/eeprom_read.ino
@@ -15,9 +15,6 @@ byte value;
 void setup() {
   // initialize serial and wait for port to open:
   Serial.begin(115200);
-  while (!Serial) {
-    ; // wait for serial port to connect. Needed for Leonardo only
-  }
   EEPROM.begin(512);
 }
 
diff --git a/libraries/ESP8266HTTPClient/examples/PostHttpClient/PostHttpClient.ino b/libraries/ESP8266HTTPClient/examples/PostHttpClient/PostHttpClient.ino
index 94d57bdbf4..936e235eeb 100644
--- a/libraries/ESP8266HTTPClient/examples/PostHttpClient/PostHttpClient.ino
+++ b/libraries/ESP8266HTTPClient/examples/PostHttpClient/PostHttpClient.ino
@@ -8,8 +8,6 @@
 #include <ESP8266WiFi.h>
 #include <ESP8266HTTPClient.h>
 
-#define USE_SERIAL Serial
-
 /* this can be run with an emulated server on host:
         cd esp8266-core-root-dir
         cd tests/host
@@ -27,21 +25,21 @@
 
 void setup() {
 
-  USE_SERIAL.begin(115200);
+  Serial.begin(115200);
 
-  USE_SERIAL.println();
-  USE_SERIAL.println();
-  USE_SERIAL.println();
+  Serial.println();
+  Serial.println();
+  Serial.println();
 
   WiFi.begin(STASSID, STAPSK);
 
   while (WiFi.status() != WL_CONNECTED) {
     delay(500);
-    USE_SERIAL.print(".");
+    Serial.print(".");
   }
-  USE_SERIAL.println("");
-  USE_SERIAL.print("Connected! IP address: ");
-  USE_SERIAL.println(WiFi.localIP());
+  Serial.println("");
+  Serial.print("Connected! IP address: ");
+  Serial.println(WiFi.localIP());
 
 }
 
@@ -52,29 +50,29 @@ void loop() {
     WiFiClient client;
     HTTPClient http;
 
-    USE_SERIAL.print("[HTTP] begin...\n");
+    Serial.print("[HTTP] begin...\n");
     // configure traged server and url
     http.begin(client, "http://" SERVER_IP "/postplain/"); //HTTP
     http.addHeader("Content-Type", "application/json");
 
-    USE_SERIAL.print("[HTTP] POST...\n");
+    Serial.print("[HTTP] POST...\n");
     // start connection and send HTTP header and body
     int httpCode = http.POST("{\"hello\":\"world\"}");
 
     // httpCode will be negative on error
     if (httpCode > 0) {
       // HTTP header has been send and Server response header has been handled
-      USE_SERIAL.printf("[HTTP] POST... code: %d\n", httpCode);
+      Serial.printf("[HTTP] POST... code: %d\n", httpCode);
 
       // file found at server
       if (httpCode == HTTP_CODE_OK) {
         const String& payload = http.getString();
-        USE_SERIAL.println("received payload:\n<<");
-        USE_SERIAL.println(payload);
-        USE_SERIAL.println(">>");
+        Serial.println("received payload:\n<<");
+        Serial.println(payload);
+        Serial.println(">>");
       }
     } else {
-      USE_SERIAL.printf("[HTTP] POST... failed, error: %s\n", http.errorToString(httpCode).c_str());
+      Serial.printf("[HTTP] POST... failed, error: %s\n", http.errorToString(httpCode).c_str());
     }
 
     http.end();
diff --git a/libraries/ESP8266WebServer/examples/FSBrowser/FSBrowser.ino b/libraries/ESP8266WebServer/examples/FSBrowser/FSBrowser.ino
index beebeb0146..f6aff52c7d 100644
--- a/libraries/ESP8266WebServer/examples/FSBrowser/FSBrowser.ino
+++ b/libraries/ESP8266WebServer/examples/FSBrowser/FSBrowser.ino
@@ -25,8 +25,8 @@
 
 // Select the FileSystem by uncommenting one of the lines below
 
-#define USE_SPIFFS
-//#define USE_LITTLEFS
+//#define USE_SPIFFS
+#define USE_LITTLEFS
 //#define USE_SDFS
 
 // Uncomment the following line to embed a version of the web page in the code
diff --git a/libraries/ESP8266WebServer/examples/HttpHashCredAuth/HttpHashCredAuth.ino b/libraries/ESP8266WebServer/examples/HttpHashCredAuth/HttpHashCredAuth.ino
index e37295b060..c2ceaca53d 100644
--- a/libraries/ESP8266WebServer/examples/HttpHashCredAuth/HttpHashCredAuth.ino
+++ b/libraries/ESP8266WebServer/examples/HttpHashCredAuth/HttpHashCredAuth.ino
@@ -7,10 +7,11 @@
   1. Creating a secure web server using ESP8266ESP8266WebServerSecure
   2. Use of HTTP authentication on this secure server
   3. A simple web interface to allow an authenticated user to change Credentials
-  4. Persisting those credentials through a reboot of the ESP by saving them to SPIFFS without storing them as plain text
+  4. Persisting those credentials through a reboot of the ESP by saving them to LittleFS without storing them as plain text
 */
 
 #include <FS.h>
+#include <LittleFS.h>
 #include <ESP8266WiFi.h>
 #include <ESP8266WebServerSecure.h>
 
@@ -23,8 +24,8 @@
 const char* ssid = STASSID;
 const char* wifi_pw = STAPSK;
 
-const String file_credentials = R"(/credentials.txt)"; //SPIFFS file name for the saved credentials
-const String change_creds =  "changecreds"; //address for a credential change
+const String file_credentials = R"(/credentials.txt)"; // LittleFS file name for the saved credentials
+const String change_creds =  "changecreds";            // Address for a credential change
 
 //The ESP8266WebServerSecure requires an encryption certificate and matching key.
 //These can generated with the bash script available in the ESP8266 Arduino repository.
@@ -83,7 +84,7 @@ gz5JWYhbD6c38khSzJb0pNXCo3EuYAVa36kDM96k1BtWuhRS10Q1VXk=
 
 ESP8266WebServerSecure server(443);
 
-//These are temporary credentials that will only be used if none are found saved in SPIFFS.
+//These are temporary credentials that will only be used if none are found saved in LittleFS.
 String login = "admin";
 const String realm = "global";
 String H1 = "";
@@ -92,9 +93,9 @@ String authentication_failed = "User authentication has failed.";
 void setup() {
   Serial.begin(115200);
 
-  //Initialize SPIFFS to save credentials
-  if(!SPIFFS.begin()){
-		Serial.println("SPIFFS initialization error, programmer flash configured?");
+  //Initialize LittleFS to save credentials
+  if(!LittleFS.begin()){
+		Serial.println("LittleFS initialization error, programmer flash configured?");
     ESP.restart();
 	}
 
@@ -187,16 +188,16 @@ void showcredentialpage(){
   server.send(200, "text/html", page);
 }
 
-//Saves credentials to SPIFFS
+//Saves credentials to LittleFS
 void savecredentials(String new_login, String new_password)
 {
   //Set global variables to new values
   login=new_login;
   H1=ESP8266WebServer::credentialHash(new_login,realm,new_password);
 
-  //Save new values to SPIFFS for loading on next reboot
+  //Save new values to LittleFS for loading on next reboot
   Serial.println("Saving credentials.");
-  File f=SPIFFS.open(file_credentials,"w"); //open as a brand new file, discard old contents
+  File f=LittleFS.open(file_credentials,"w"); //open as a brand new file, discard old contents
   if(f){
     Serial.println("Modifying credentials in file system.");
     f.println(login);
@@ -208,12 +209,12 @@ void savecredentials(String new_login, String new_password)
   Serial.println("Credentials saved.");
 }
 
-//loads credentials from SPIFFS
+//loads credentials from LittleFS
 void loadcredentials()
 {
   Serial.println("Searching for credentials.");
   File f;
-  f=SPIFFS.open(file_credentials,"r");
+  f=LittleFS.open(file_credentials,"r");
   if(f){
     Serial.println("Loading credentials from file system.");
     String mod=f.readString(); //read the file to a String
diff --git a/libraries/ESP8266WiFi/examples/BearSSL_CertStore/BearSSL_CertStore.ino b/libraries/ESP8266WiFi/examples/BearSSL_CertStore/BearSSL_CertStore.ino
index 20a8a445a9..48bfd0e2c2 100644
--- a/libraries/ESP8266WiFi/examples/BearSSL_CertStore/BearSSL_CertStore.ino
+++ b/libraries/ESP8266WiFi/examples/BearSSL_CertStore/BearSSL_CertStore.ino
@@ -2,11 +2,11 @@
 //
 // Before running, you must download the set of certs using
 // the script "certs-from-mozilla.py" (no parameters)
-// and then uploading the generated .AR file to SPIFFS or SD.
+// and then uploading the generated .AR file to LittleFS or SD.
 //
 // You do not need to generate the ".IDX" file listed below,
 // it is generated automatically when the CertStore object
-// is created and written to SD or SPIFFS by the ESP8266.
+// is created and written to SD or LittleFS by the ESP8266.
 //
 // Why would you need a CertStore?
 //
@@ -37,6 +37,7 @@
 #include <CertStoreBearSSL.h>
 #include <time.h>
 #include <FS.h>
+#include <LittleFS.h>
 
 #ifndef STASSID
 #define STASSID "your-ssid"
@@ -117,8 +118,7 @@ void setup() {
   Serial.println();
   Serial.println();
 
-  SPIFFS.begin();
-  // If using a SD card or LittleFS, call the appropriate ::begin instead
+  LittleFS.begin();
 
   // We start by connecting to a WiFi network
   Serial.print("Connecting to ");
@@ -138,10 +138,10 @@ void setup() {
 
   setClock(); // Required for X.509 validation
 
-  int numCerts = certStore.initCertStore(SPIFFS, PSTR("/certs.idx"), PSTR("/certs.ar"));
+  int numCerts = certStore.initCertStore(LittleFS, PSTR("/certs.idx"), PSTR("/certs.ar"));
   Serial.printf("Number of CA certs read: %d\n", numCerts);
   if (numCerts == 0) {
-    Serial.printf("No certs found. Did you run certs-from-mozilla.py and upload the SPIFFS directory before running?\n");
+    Serial.printf("No certs found. Did you run certs-from-mozilla.py and upload the LittleFS directory before running?\n");
     return; // Can't connect to anything w/o certs!
   }
 
diff --git a/libraries/ESP8266WiFi/examples/BearSSL_CertStore/certs-from-mozilla.py b/libraries/ESP8266WiFi/examples/BearSSL_CertStore/certs-from-mozilla.py
index e423bc25b9..556acb70fa 100755
--- a/libraries/ESP8266WiFi/examples/BearSSL_CertStore/certs-from-mozilla.py
+++ b/libraries/ESP8266WiFi/examples/BearSSL_CertStore/certs-from-mozilla.py
@@ -3,7 +3,7 @@
 # This script pulls the list of Mozilla trusted certificate authorities
 # from the web at the "mozurl" below, parses the file to grab the PEM
 # for each cert, and then generates DER files in a new ./data directory
-# Upload these to a SPIFFS filesystem and use the CertManager to parse
+# Upload these to an on-chip filesystem and use the CertManager to parse
 # and use them for your outgoing SSL connections.
 #
 # Script by Earle F. Philhower, III.  Released to the public domain.
diff --git a/libraries/ESP8266WiFi/keywords.txt b/libraries/ESP8266WiFi/keywords.txt
index 16eea24227..ec3c0228bd 100644
--- a/libraries/ESP8266WiFi/keywords.txt
+++ b/libraries/ESP8266WiFi/keywords.txt
@@ -23,8 +23,6 @@ BearSSL	KEYWORD1
 X509List	KEYWORD1
 PrivateKey	KEYWORD1
 PublicKey	KEYWORD1
-CertStoreSPIFFSBearSSL	KEYWORD1
-CertStoreSDBearSSL	KEYWORD1
 Session	KEYWORD1
 ESP8266WiFiGratuitous	KEYWORD1
 
diff --git a/libraries/ESP8266WiFi/src/CertStoreBearSSL.h b/libraries/ESP8266WiFi/src/CertStoreBearSSL.h
index 76d4966e6a..ed3852e2ad 100644
--- a/libraries/ESP8266WiFi/src/CertStoreBearSSL.h
+++ b/libraries/ESP8266WiFi/src/CertStoreBearSSL.h
@@ -26,7 +26,7 @@
 #include <FS.h>
 
 // Base class for the certificate stores, which allow use
-// of a large set of certificates stored on SPIFFS of SD card to
+// of a large set of certificates stored on FS or SD card to
 // be dynamically used when validating a X509 certificate
 
 namespace BearSSL {
diff --git a/libraries/ESP8266httpUpdate/examples/httpUpdate/httpUpdate.ino b/libraries/ESP8266httpUpdate/examples/httpUpdate/httpUpdate.ino
index 69ed71fe6b..19c555a235 100644
--- a/libraries/ESP8266httpUpdate/examples/httpUpdate/httpUpdate.ino
+++ b/libraries/ESP8266httpUpdate/examples/httpUpdate/httpUpdate.ino
@@ -13,8 +13,6 @@
 #include <ESP8266HTTPClient.h>
 #include <ESP8266httpUpdate.h>
 
-#define USE_SERIAL Serial
-
 #ifndef APSSID
 #define APSSID "APSSID"
 #define APPSK  "APPSK"
@@ -24,16 +22,16 @@ ESP8266WiFiMulti WiFiMulti;
 
 void setup() {
 
-  USE_SERIAL.begin(115200);
-  // USE_SERIAL.setDebugOutput(true);
+  Serial.begin(115200);
+  // Serial.setDebugOutput(true);
 
-  USE_SERIAL.println();
-  USE_SERIAL.println();
-  USE_SERIAL.println();
+  Serial.println();
+  Serial.println();
+  Serial.println();
 
   for (uint8_t t = 4; t > 0; t--) {
-    USE_SERIAL.printf("[SETUP] WAIT %d...\n", t);
-    USE_SERIAL.flush();
+    Serial.printf("[SETUP] WAIT %d...\n", t);
+    Serial.flush();
     delay(1000);
   }
 
@@ -44,19 +42,19 @@ void setup() {
 }
 
 void update_started() {
-  USE_SERIAL.println("CALLBACK:  HTTP update process started");
+  Serial.println("CALLBACK:  HTTP update process started");
 }
 
 void update_finished() {
-  USE_SERIAL.println("CALLBACK:  HTTP update process finished");
+  Serial.println("CALLBACK:  HTTP update process finished");
 }
 
 void update_progress(int cur, int total) {
-  USE_SERIAL.printf("CALLBACK:  HTTP update process at %d of %d bytes...\n", cur, total);
+  Serial.printf("CALLBACK:  HTTP update process at %d of %d bytes...\n", cur, total);
 }
 
 void update_error(int err) {
-  USE_SERIAL.printf("CALLBACK:  HTTP update fatal error code %d\n", err);
+  Serial.printf("CALLBACK:  HTTP update fatal error code %d\n", err);
 }
 
 
@@ -86,15 +84,15 @@ void loop() {
 
     switch (ret) {
       case HTTP_UPDATE_FAILED:
-        USE_SERIAL.printf("HTTP_UPDATE_FAILD Error (%d): %s\n", ESPhttpUpdate.getLastError(), ESPhttpUpdate.getLastErrorString().c_str());
+        Serial.printf("HTTP_UPDATE_FAILD Error (%d): %s\n", ESPhttpUpdate.getLastError(), ESPhttpUpdate.getLastErrorString().c_str());
         break;
 
       case HTTP_UPDATE_NO_UPDATES:
-        USE_SERIAL.println("HTTP_UPDATE_NO_UPDATES");
+        Serial.println("HTTP_UPDATE_NO_UPDATES");
         break;
 
       case HTTP_UPDATE_OK:
-        USE_SERIAL.println("HTTP_UPDATE_OK");
+        Serial.println("HTTP_UPDATE_OK");
         break;
     }
   }
diff --git a/libraries/ESP8266httpUpdate/examples/httpUpdateSPIFFS/httpUpdateSPIFFS.ino b/libraries/ESP8266httpUpdate/examples/httpUpdateLittleFS/httpUpdateLittleFS.ino
similarity index 66%
rename from libraries/ESP8266httpUpdate/examples/httpUpdateSPIFFS/httpUpdateSPIFFS.ino
rename to libraries/ESP8266httpUpdate/examples/httpUpdateLittleFS/httpUpdateLittleFS.ino
index 8e035fde63..6541d047fd 100644
--- a/libraries/ESP8266httpUpdate/examples/httpUpdateSPIFFS/httpUpdateSPIFFS.ino
+++ b/libraries/ESP8266httpUpdate/examples/httpUpdateLittleFS/httpUpdateLittleFS.ino
@@ -1,5 +1,5 @@
 /**
-   httpUpdateSPIFFS.ino
+   httpUpdateLittleFS.ino
 
     Created on: 05.12.2015
 
@@ -13,8 +13,6 @@
 #include <ESP8266HTTPClient.h>
 #include <ESP8266httpUpdate.h>
 
-#define USE_SERIAL Serial
-
 ESP8266WiFiMulti WiFiMulti;
 
 #ifndef APSSID
@@ -24,16 +22,16 @@ ESP8266WiFiMulti WiFiMulti;
 
 void setup() {
 
-  USE_SERIAL.begin(115200);
-  // USE_SERIAL.setDebugOutput(true);
+  Serial.begin(115200);
+  // Serial.setDebugOutput(true);
 
-  USE_SERIAL.println();
-  USE_SERIAL.println();
-  USE_SERIAL.println();
+  Serial.println();
+  Serial.println();
+  Serial.println();
 
   for (uint8_t t = 4; t > 0; t--) {
-    USE_SERIAL.printf("[SETUP] WAIT %d...\n", t);
-    USE_SERIAL.flush();
+    Serial.printf("[SETUP] WAIT %d...\n", t);
+    Serial.flush();
     delay(1000);
   }
 
@@ -46,7 +44,7 @@ void loop() {
   // wait for WiFi connection
   if ((WiFiMulti.run() == WL_CONNECTED)) {
 
-    USE_SERIAL.println("Update SPIFFS...");
+    Serial.println("Update LittleFS...");
 
     WiFiClient client;
 
@@ -58,22 +56,22 @@ void loop() {
     // value is used to put the LED on. If the LED is on with HIGH, that value should be passed
     ESPhttpUpdate.setLedPin(LED_BUILTIN, LOW);
 
-    t_httpUpdate_return ret = ESPhttpUpdate.updateSpiffs(client, "http://server/spiffs.bin");
+    t_httpUpdate_return ret = ESPhttpUpdate.updateFS(client, "http://server/spiffs.bin");
     if (ret == HTTP_UPDATE_OK) {
-      USE_SERIAL.println("Update sketch...");
+      Serial.println("Update sketch...");
       ret = ESPhttpUpdate.update(client, "http://server/file.bin");
 
       switch (ret) {
         case HTTP_UPDATE_FAILED:
-          USE_SERIAL.printf("HTTP_UPDATE_FAILED Error (%d): %s", ESPhttpUpdate.getLastError(), ESPhttpUpdate.getLastErrorString().c_str());
+          Serial.printf("HTTP_UPDATE_FAILED Error (%d): %s", ESPhttpUpdate.getLastError(), ESPhttpUpdate.getLastErrorString().c_str());
           break;
 
         case HTTP_UPDATE_NO_UPDATES:
-          USE_SERIAL.println("HTTP_UPDATE_NO_UPDATES");
+          Serial.println("HTTP_UPDATE_NO_UPDATES");
           break;
 
         case HTTP_UPDATE_OK:
-          USE_SERIAL.println("HTTP_UPDATE_OK");
+          Serial.println("HTTP_UPDATE_OK");
           break;
       }
     }
diff --git a/libraries/ESP8266httpUpdate/examples/httpUpdateSecure/httpUpdateSecure.ino b/libraries/ESP8266httpUpdate/examples/httpUpdateSecure/httpUpdateSecure.ino
index 9eba1e5140..beb613897c 100644
--- a/libraries/ESP8266httpUpdate/examples/httpUpdateSecure/httpUpdateSecure.ino
+++ b/libraries/ESP8266httpUpdate/examples/httpUpdateSecure/httpUpdateSecure.ino
@@ -14,8 +14,7 @@
 #include <time.h>
 
 #include <FS.h>
-
-#define USE_SERIAL Serial
+#include <LittleFS.h>
 
 #ifndef APSSID
 #define APSSID "APSSID"
@@ -34,46 +33,47 @@ BearSSL::CertStore certStore;
 void setClock() {
   configTime(0, 0, "pool.ntp.org", "time.nist.gov");  // UTC
 
-  USE_SERIAL.print(F("Waiting for NTP time sync: "));
+  Serial.print(F("Waiting for NTP time sync: "));
   time_t now = time(nullptr);
   while (now < 8 * 3600 * 2) {
     yield();
     delay(500);
-    USE_SERIAL.print(F("."));
+    Serial.print(F("."));
     now = time(nullptr);
   }
 
-  USE_SERIAL.println(F(""));
+  Serial.println(F(""));
   struct tm timeinfo;
   gmtime_r(&now, &timeinfo);
-  USE_SERIAL.print(F("Current time: "));
-  USE_SERIAL.print(asctime(&timeinfo));
+  Serial.print(F("Current time: "));
+  Serial.print(asctime(&timeinfo));
 }
 
 void setup() {
 
-  USE_SERIAL.begin(115200);
-  // USE_SERIAL.setDebugOutput(true);
+  Serial.begin(115200);
+  // Serial.setDebugOutput(true);
 
-  USE_SERIAL.println();
-  USE_SERIAL.println();
-  USE_SERIAL.println();
+  Serial.println();
+  Serial.println();
+  Serial.println();
 
   for (uint8_t t = 4; t > 0; t--) {
-    USE_SERIAL.printf("[SETUP] WAIT %d...\n", t);
-    USE_SERIAL.flush();
+    Serial.printf("[SETUP] WAIT %d...\n", t);
+    Serial.flush();
     delay(1000);
   }
 
   WiFi.mode(WIFI_STA);
   WiFiMulti.addAP(APSSID, APPSK);
 
-  SPIFFS.begin();
+  LittleFS.begin();
 
-  int numCerts = certStore.initCertStore(SPIFFS, PSTR("/certs.idx"), PSTR("/certs.ar"));
-  USE_SERIAL.print(F("Number of CA certs read: ")); USE_SERIAL.println(numCerts);
+  int numCerts = certStore.initCertStore(LittleFS, PSTR("/certs.idx"), PSTR("/certs.ar"));
+  Serial.print(F("Number of CA certs read: "));
+  Serial.println(numCerts);
   if (numCerts == 0) {
-    USE_SERIAL.println(F("No certs found. Did you run certs-from-mozill.py and upload the SPIFFS directory before running?"));
+    Serial.println(F("No certs found. Did you run certs-from-mozill.py and upload the LittleFS directory before running?"));
     return; // Can't connect to anything w/o certs!
   }
 }
@@ -86,7 +86,7 @@ void loop() {
 
     BearSSL::WiFiClientSecure client;
     bool mfln = client.probeMaxFragmentLength("server", 443, 1024);  // server must be the same as in ESPhttpUpdate.update()
-    USE_SERIAL.printf("MFLN supported: %s\n", mfln ? "yes" : "no");
+    Serial.printf("MFLN supported: %s\n", mfln ? "yes" : "no");
     if (mfln) {
       client.setBufferSizes(1024, 1024);
     }
@@ -107,15 +107,15 @@ void loop() {
 
     switch (ret) {
       case HTTP_UPDATE_FAILED:
-        USE_SERIAL.printf("HTTP_UPDATE_FAILED Error (%d): %s\n", ESPhttpUpdate.getLastError(), ESPhttpUpdate.getLastErrorString().c_str());
+        Serial.printf("HTTP_UPDATE_FAILED Error (%d): %s\n", ESPhttpUpdate.getLastError(), ESPhttpUpdate.getLastErrorString().c_str());
         break;
 
       case HTTP_UPDATE_NO_UPDATES:
-        USE_SERIAL.println("HTTP_UPDATE_NO_UPDATES");
+        Serial.println("HTTP_UPDATE_NO_UPDATES");
         break;
 
       case HTTP_UPDATE_OK:
-        USE_SERIAL.println("HTTP_UPDATE_OK");
+        Serial.println("HTTP_UPDATE_OK");
         break;
     }
   }
diff --git a/libraries/ESP8266httpUpdate/src/ESP8266httpUpdate.cpp b/libraries/ESP8266httpUpdate/src/ESP8266httpUpdate.cpp
index a7fe1934d2..f481d79a69 100755
--- a/libraries/ESP8266httpUpdate/src/ESP8266httpUpdate.cpp
+++ b/libraries/ESP8266httpUpdate/src/ESP8266httpUpdate.cpp
@@ -126,7 +126,7 @@ HTTPUpdateResult ESP8266HTTPUpdate::updateSpiffs(const String& url, const String
 }
 #endif
 
-HTTPUpdateResult ESP8266HTTPUpdate::updateSpiffs(WiFiClient& client, const String& url, const String& currentVersion)
+HTTPUpdateResult ESP8266HTTPUpdate::updateFS(WiFiClient& client, const String& url, const String& currentVersion)
 {
     HTTPClient http;
     http.begin(client, url);
diff --git a/libraries/ESP8266httpUpdate/src/ESP8266httpUpdate.h b/libraries/ESP8266httpUpdate/src/ESP8266httpUpdate.h
index ddbd307ad9..f1565cd2c6 100755
--- a/libraries/ESP8266httpUpdate/src/ESP8266httpUpdate.h
+++ b/libraries/ESP8266httpUpdate/src/ESP8266httpUpdate.h
@@ -146,7 +146,10 @@ class ESP8266HTTPUpdate
     t_httpUpdate_return updateSpiffs(const String& url, const String& currentVersion, const String& httpsFingerprint) __attribute__((deprecated));
     t_httpUpdate_return updateSpiffs(const String& url, const String& currentVersion, const uint8_t httpsFingerprint[20]) __attribute__((deprecated)); // BearSSL
 #endif
-    t_httpUpdate_return updateSpiffs(WiFiClient& client, const String& url, const String& currentVersion = "");
+    t_httpUpdate_return updateFS(WiFiClient& client, const String& url, const String& currentVersion = "");
+    t_httpUpdate_return updateSpiffs(WiFiClient& client, const String& url, const String& currentVersion = "") __attribute__((deprecated)) {
+        return updateFS(client, url, currentVersion);
+    };
 
     // Notification callbacks
     void onStart(HTTPUpdateStartCB cbOnStart)          { _cbStart = cbOnStart; }
diff --git a/libraries/ESP8266mDNS/examples/OTA-mDNS-SPIFFS/OTA-mDNS-SPIFFS.ino b/libraries/ESP8266mDNS/examples/OTA-mDNS-LittleFS/OTA-mDNS-SPIFFS.ino
similarity index 96%
rename from libraries/ESP8266mDNS/examples/OTA-mDNS-SPIFFS/OTA-mDNS-SPIFFS.ino
rename to libraries/ESP8266mDNS/examples/OTA-mDNS-LittleFS/OTA-mDNS-SPIFFS.ino
index a03b7cfbad..9d0d861474 100644
--- a/libraries/ESP8266mDNS/examples/OTA-mDNS-SPIFFS/OTA-mDNS-SPIFFS.ino
+++ b/libraries/ESP8266mDNS/examples/OTA-mDNS-LittleFS/OTA-mDNS-SPIFFS.ino
@@ -1,5 +1,5 @@
 /**
-   @file OTA-mDNS-SPIFFS.ino
+   @file OTA-mDNS-LittleFS.ino
 
    @author Pascal Gollor (http://www.pgollor.de/cms/)
    @date 2015-09-18
@@ -22,6 +22,7 @@
 #include <ESP8266mDNS.h>
 #include <WiFiUdp.h>
 #include <FS.h>
+#include <LittleFS.h>
 #include <ArduinoOTA.h>
 
 
@@ -55,7 +56,7 @@ const char* ap_default_psk = STAPSK; ///< Default PSK.
 */
 bool loadConfig(String *ssid, String *pass) {
   // open file for reading.
-  File configFile = SPIFFS.open("/cl_conf.txt", "r");
+  File configFile = LittleFS.open("/cl_conf.txt", "r");
   if (!configFile) {
     Serial.println("Failed to open cl_conf.txt.");
 
@@ -115,7 +116,7 @@ bool loadConfig(String *ssid, String *pass) {
 */
 bool saveConfig(String *ssid, String *pass) {
   // Open config file for writing.
-  File configFile = SPIFFS.open("/cl_conf.txt", "w");
+  File configFile = LittleFS.open("/cl_conf.txt", "w");
   if (!configFile) {
     Serial.println("Failed to open cl_conf.txt for writing");
 
@@ -158,7 +159,7 @@ void setup() {
 
 
   // Initialize file system.
-  if (!SPIFFS.begin()) {
+  if (!LittleFS.begin()) {
     Serial.println("Failed to mount file system");
     return;
   }
diff --git a/libraries/ESP8266mDNS/examples/OTA-mDNS-SPIFFS/data/cl_conf.txt b/libraries/ESP8266mDNS/examples/OTA-mDNS-LittleFS/data/cl_conf.txt
similarity index 100%
rename from libraries/ESP8266mDNS/examples/OTA-mDNS-SPIFFS/data/cl_conf.txt
rename to libraries/ESP8266mDNS/examples/OTA-mDNS-LittleFS/data/cl_conf.txt
diff --git a/libraries/LittleFS/examples/SpeedTest/SpeedTest.ino b/libraries/LittleFS/examples/SpeedTest/SpeedTest.ino
index 5b7dd453a0..5987e10807 100644
--- a/libraries/LittleFS/examples/SpeedTest/SpeedTest.ino
+++ b/libraries/LittleFS/examples/SpeedTest/SpeedTest.ino
@@ -1,8 +1,17 @@
 // Simple speed test for filesystem objects
 // Released to the public domain by Earle F. Philhower, III
 
+#include <FS.h>
 #include <LittleFS.h>
 
+// Choose the filesystem to test
+// WARNING:  The filesystem will be formatted at the start of the test!
+
+#define TESTFS LittleFS
+//#define TESTFS SPIFFS
+//#define TESTFS SDFS
+
+// How large of a file to test
 #define TESTSIZEKB 512
 
 void DoTest(FS *fs) {
@@ -112,12 +121,9 @@ void DoTest(FS *fs) {
 
 void setup() {
   Serial.begin(115200);
-  Serial.printf("Beginning LittleFS test\n");
-  Serial.flush();
-  DoTest(&LittleFS);
-  Serial.printf("Beginning SPIFFS test\n");
+  Serial.printf("Beginning test\n");
   Serial.flush();
-  DoTest(&SPIFFS);
+  DoTest(&TESTFS);
 }
 
 void loop() {
diff --git a/libraries/SD/examples/Datalogger/Datalogger.ino b/libraries/SD/examples/Datalogger/Datalogger.ino
index fcb7a56e13..a023b63821 100644
--- a/libraries/SD/examples/Datalogger/Datalogger.ino
+++ b/libraries/SD/examples/Datalogger/Datalogger.ino
@@ -27,11 +27,7 @@ const int chipSelect = 4;
 
 void setup() {
   // Open serial communications and wait for port to open:
-  Serial.begin(9600);
-  while (!Serial) {
-    ; // wait for serial port to connect. Needed for Leonardo only
-  }
-
+  Serial.begin(115200);
 
   Serial.print("Initializing SD card...");
 
diff --git a/libraries/SD/examples/DumpFile/DumpFile.ino b/libraries/SD/examples/DumpFile/DumpFile.ino
index 42bd8bcbb0..3574652890 100644
--- a/libraries/SD/examples/DumpFile/DumpFile.ino
+++ b/libraries/SD/examples/DumpFile/DumpFile.ino
@@ -27,11 +27,7 @@ const int chipSelect = 4;
 
 void setup() {
   // Open serial communications and wait for port to open:
-  Serial.begin(9600);
-  while (!Serial) {
-    ; // wait for serial port to connect. Needed for Leonardo only
-  }
-
+  Serial.begin(115200);
 
   Serial.print("Initializing SD card...");
 
diff --git a/libraries/SD/examples/Files/Files.ino b/libraries/SD/examples/Files/Files.ino
index cb2c1f1d2a..1c1b83ec20 100644
--- a/libraries/SD/examples/Files/Files.ino
+++ b/libraries/SD/examples/Files/Files.ino
@@ -24,11 +24,7 @@ File myFile;
 
 void setup() {
   // Open serial communications and wait for port to open:
-  Serial.begin(9600);
-  while (!Serial) {
-    ; // wait for serial port to connect. Needed for Leonardo only
-  }
-
+  Serial.begin(115200);
 
   Serial.print("Initializing SD card...");
 
diff --git a/libraries/SD/examples/ReadWrite/ReadWrite.ino b/libraries/SD/examples/ReadWrite/ReadWrite.ino
index cd63aa554c..7aa9a40c4b 100644
--- a/libraries/SD/examples/ReadWrite/ReadWrite.ino
+++ b/libraries/SD/examples/ReadWrite/ReadWrite.ino
@@ -25,11 +25,7 @@ File myFile;
 
 void setup() {
   // Open serial communications and wait for port to open:
-  Serial.begin(9600);
-  while (!Serial) {
-    ; // wait for serial port to connect. Needed for Leonardo only
-  }
-
+  Serial.begin(115200);
 
   Serial.print("Initializing SD card...");
 
diff --git a/libraries/TFT_Touch_Shield_V2/examples/tftbmp/tftbmp.ino b/libraries/TFT_Touch_Shield_V2/examples/tftbmp/tftbmp.ino
index 2bfc9f1473..4176de59dc 100644
--- a/libraries/TFT_Touch_Shield_V2/examples/tftbmp/tftbmp.ino
+++ b/libraries/TFT_Touch_Shield_V2/examples/tftbmp/tftbmp.ino
@@ -42,7 +42,7 @@ File bmpFile;
 
 void setup() {
 
-  Serial.begin(9600);
+  Serial.begin(115200);
 
   pinMode(PIN_SD_CS, OUTPUT);
   digitalWrite(PIN_SD_CS, HIGH);
diff --git a/libraries/esp8266/examples/ConfigFile/ConfigFile.ino b/libraries/esp8266/examples/ConfigFile/ConfigFile.ino
index 77bbfabaa9..cb1d25be07 100644
--- a/libraries/esp8266/examples/ConfigFile/ConfigFile.ino
+++ b/libraries/esp8266/examples/ConfigFile/ConfigFile.ino
@@ -9,9 +9,10 @@
 
 #include <ArduinoJson.h>
 #include "FS.h"
+#include <LittleFS.h>
 
 bool loadConfig() {
-  File configFile = SPIFFS.open("/config.json", "r");
+  File configFile = LittleFS.open("/config.json", "r");
   if (!configFile) {
     Serial.println("Failed to open config file");
     return false;
@@ -56,7 +57,7 @@ bool saveConfig() {
   doc["serverName"] = "api.example.com";
   doc["accessToken"] = "128du9as8du12eoue8da98h123ueh9h98";
 
-  File configFile = SPIFFS.open("/config.json", "w");
+  File configFile = LittleFS.open("/config.json", "w");
   if (!configFile) {
     Serial.println("Failed to open config file for writing");
     return false;
@@ -72,7 +73,7 @@ void setup() {
   delay(1000);
   Serial.println("Mounting FS...");
 
-  if (!SPIFFS.begin()) {
+  if (!LittleFS.begin()) {
     Serial.println("Failed to mount file system");
     return;
   }
diff --git a/tests/host/common/MockUART.cpp b/tests/host/common/MockUART.cpp
index 023c775bfc..825a4dc0d6 100644
--- a/tests/host/common/MockUART.cpp
+++ b/tests/host/common/MockUART.cpp
@@ -88,7 +88,10 @@ uart_do_write_char(const int uart_nr, char c)
 		}
 		else
 		{
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-result"
 			write(uart_nr + 1, &c, 1);
+#pragma GCC diagnostic pop
 			w = true;
 		}
 	}
diff --git a/tests/host/common/spiffs_mock.cpp b/tests/host/common/spiffs_mock.cpp
index 3e85fa06ab..8e73626194 100644
--- a/tests/host/common/spiffs_mock.cpp
+++ b/tests/host/common/spiffs_mock.cpp
@@ -31,6 +31,9 @@
 
 #define SPIFFS_FILE_NAME "spiffs.bin"
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
 FS SPIFFS(nullptr);
 
 SpiffsMock::SpiffsMock(ssize_t fs_size, size_t fs_block, size_t fs_page, const String& storage)
@@ -126,3 +129,6 @@ void SpiffsMock::save ()
     if (::close(fs) == -1)
         fprintf(stderr, "SPIFFS: closing %s: %s\n", m_storage.c_str(), strerror(errno));
 }
+
+#pragma GCC diagnostic pop
+
diff --git a/tests/host/core/test_Print.cpp b/tests/host/core/test_Print.cpp
index c3cb2f5cd0..e58539c59e 100644
--- a/tests/host/core/test_Print.cpp
+++ b/tests/host/core/test_Print.cpp
@@ -16,15 +16,16 @@
 #include <catch.hpp>
 #include <string.h>
 #include <FS.h>
-#include "../common/spiffs_mock.h"
+#include <LittleFS.h>
+#include "../common/littlefs_mock.h"
 #include <spiffs/spiffs.h>
 
-// Use a SPIFFS file because we can't instantiate a virtual class like Print
+// Use a LittleFS file because we can't instantiate a virtual class like Print
 TEST_CASE("Print::write overrides all compile properly", "[core][Print]")
 {
-    SPIFFS_MOCK_DECLARE(64, 8, 512, "");
-    REQUIRE(SPIFFS.begin());
-    auto p = SPIFFS.open("test.bin", "w");
+    LITTLEFS_MOCK_DECLARE(64, 8, 512, "");
+    REQUIRE(LittleFS.begin());
+    auto p = LittleFS.open("test.bin", "w");
     REQUIRE(p);
     uint8_t    uint8 = 1;
     uint16_t  uint16 = 2;
@@ -56,7 +57,7 @@ TEST_CASE("Print::write overrides all compile properly", "[core][Print]")
     p.write(1);
     p.close();
 
-    p = SPIFFS.open("test.bin", "r");
+    p = LittleFS.open("test.bin", "r");
     REQUIRE(p);
     uint8_t buff[16];
     int len = p.read(buff, 16);
diff --git a/tests/host/fs/test_fs.cpp b/tests/host/fs/test_fs.cpp
index 28dd0bab5b..fb73a6a271 100644
--- a/tests/host/fs/test_fs.cpp
+++ b/tests/host/fs/test_fs.cpp
@@ -26,6 +26,9 @@
 
 
 namespace spiffs_test {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
 #define FSTYPE SPIFFS
 #define TESTPRE "SPIFFS - "
 #define TESTPAT "[fs]"
@@ -54,6 +57,7 @@ TEST_CASE("SPIFFS checks the config object passed in", "[fs]")
     REQUIRE_FALSE(SPIFFS.setConfig(d));
     REQUIRE_FALSE(LittleFS.setConfig(l));
 }
+#pragma GCC diagnostic pop
 
 };
 
diff --git a/tools/boards.txt.py b/tools/boards.txt.py
index d33cbe1fc9..8263191495 100755
--- a/tools/boards.txt.py
+++ b/tools/boards.txt.py
@@ -29,7 +29,7 @@
 #            resetmethod_menu_extra      menus for additional reset methods
 #            crystalfreq/flashfreq_menu: menus for crystal/flash frequency selection
 #            flashmode_menu:             menus for flashmode selection (dio/dout/qio/qout)
-#            512K/1M/2M/4M/8M/16M:       menus for flash & SPIFFS size
+#            512K/1M/2M/4M/8M/16M:       menus for flash & FS size
 #            lwip/lwip2                  menus for available lwip versions
 
 from __future__ import print_function
@@ -613,7 +613,7 @@
             '~~~~~~~~~~~~~~~~~~~~~~~~~~',
             '',
             '- Card: "WEMOS D1 Mini Lite"',
-            '- Flash Size: "1M (512K SPIFFS)"',
+            '- Flash Size: "1M (512K FS)"',
             '- CPU Frequency: "80 Mhz"',
           # '- Upload Speed: "230400"',
             '',
@@ -696,7 +696,7 @@
         'opts': collections.OrderedDict([
             ( '.build.board', 'WIFINFO' ),
             ( '.build.variant', 'wifinfo' ),
-            ( '.menu.ESPModule.ESP07192', 'ESP07 (1M/192K SPIFFS)' ),
+            ( '.menu.ESPModule.ESP07192', 'ESP07 (1M/192K FS)' ),
             ( '.menu.ESPModule.ESP07192.build.board', 'ESP8266_ESP07' ),
             ( '.menu.ESPModule.ESP07192.build.flash_size', '1M' ),
             ( '.menu.ESPModule.ESP07192.build.flash_ld', 'eagle.flash.1m192.ld' ),
@@ -704,7 +704,7 @@
             ( '.menu.ESPModule.ESP07192.build.spiffs_end', '0xFB000' ),
             ( '.menu.ESPModule.ESP07192.build.spiffs_blocksize', '4096' ),
             ( '.menu.ESPModule.ESP07192.upload.maximum_size', '827376' ),
-            ( '.menu.ESPModule.ESP12', 'ESP12 (4M/1M SPIFFS)' ),
+            ( '.menu.ESPModule.ESP12', 'ESP12 (4M/1M FS)' ),
             ( '.menu.ESPModule.ESP12.build.board', 'ESP8266_ESP12' ),
             ( '.menu.ESPModule.ESP12.build.flash_size', '4M' ),
             ( '.menu.ESPModule.ESP12.build.flash_ld', 'eagle.flash.4m1m.ld' ),
@@ -1316,7 +1316,7 @@ def flash_map (flashsize_kb, fs_kb = 0):
     else:
         fs_blocksize = 8192
 
-    # Adjust SPIFFS_end to be a multiple of the block size
+    # Adjust FS_end to be a multiple of the block size
     fs_end = fs_blocksize * (int)((fs_end - fs_start)/fs_blocksize) + fs_start;
 
     max_ota_size = min(max_upload_size, fs_start / 2) # =(max_upload_size+empty_size)/2