ESP8266 core for Arduino
aerlon and devyte WiFi Mesh Update 2.1 (#5157)
* - Add assert in HelloMesh.ino for invalid transmission status.
- Make uint64ToString and stringToUint64 methods into stand-alone type conversion functions.
- Add getters and setters for requestHandler and responseHandler.
- Polish HelloMesh.ino code by adding networkIndex as networkFilter loop variable and switching networkFilter definition position.
- Add initial WiFi.disconnect() in HelloMesh.ino setup() function to ensure smooth WiFi operation.
- Add latestTransmissionSuccessful() convenience method.
- Change default WiFi mode to WIFI_STA and improve handling of WiFi mode (fixes issue #5071).
- Add checks to methods that change AP properties to avoid unnecessary AP restarts.
- Add getter for ESP8266WiFiMesh SSID and getters and setters for ESP8266WiFiMesh settings related to hidden SSID usage, max station connections allowed per AP and WiFi timeouts.
- Make waitForClientTransmission method use more accurate timekeeping.
- Improve type usage.
- Improve comments.
- Update, keywords.txt and

* Make getter and setter order consistent throughout code.

* - Fix active AP getting turned off when calling begin().
- Fix crash bug due to WiFiServer duplication when using the ESP8266WiFiMesh copy constructor with the AP controller as argument, under certain circumstances.

* - Move non performance-sensitive Strings to flash memory to save RAM.

- Add comments explaining F(), FPSTR() and PROGMEM.

- Fix formatting.

* Remove the uint64ToString and stringToUint64 methods from the ESP8266WiFiMesh class since they are now stand-alone functions in the TypeConversionFunctions files.

* Change the minimum valid argument value of the setMaxAPStations method to 0, since this value is also supported by the ESP8266.

* Fix compiler warning.
Latest commit 88bd26b Sep 24, 2018

Arduino core for ESP8266 WiFi chip

This project brings support for ESP8266 chip to the Arduino environment. It lets you write sketches using familiar Arduino functions and libraries, and run them directly on ESP8266, no external microcontroller required.

ESP8266 Arduino core comes with libraries to communicate over WiFi using TCP and UDP, set up HTTP, mDNS, SSDP, and DNS servers, do OTA updates, use a file system in flash memory, work with SD cards, servos, SPI and I2C peripherals.


Installing with Boards Manager

Starting with 1.6.4, Arduino allows installation of third-party platform packages using Boards Manager. We have packages available for Windows, Mac OS, and Linux (32 and 64 bit).

  • Install the current upstream Arduino IDE at the 1.8 level or later. The current version is at the Arduino website.
  • Start Arduino and open Preferences window.
  • Enter into Additional Board Manager URLs field. You can add multiple URLs, separating them with commas.
  • Open Boards Manager from Tools > Board menu and install esp8266 platform (and don't forget to select your ESP8266 board from Tools > Board menu after installation).

Latest release Latest release

Boards manager link:


Using git version

Linux build status

  • Install the current upstream Arduino IDE at the 1.8 level or later. The current version is at the Arduino website.
  • Go to Arduino application directory
    • For Mac OS X, it is showing as the Arduino icon.
      This location may be your ~/Downloads, ~/Desktop or even /Applications.
      cd <application-directory>/
  • Clone this repository into hardware/esp8266com/esp8266 directory (or clone it elsewhere and create a symlink)
cd hardware
mkdir esp8266com
cd esp8266com
git clone esp8266
  • Download binary tools (you need Python 2.7)
cd esp8266/tools
  • Restart Arduino

Using PlatformIO

PlatformIO is an open source ecosystem for IoT development with cross platform build system, library manager and full support for Espressif (ESP8266) development. It works on the popular host OS: macOS, Windows, Linux 32/64, Linux ARM (like Raspberry Pi, BeagleBone, CubieBoard).

Building with make

makeEspArduino is a generic makefile for any ESP8266 Arduino project. Using make instead of the Arduino IDE makes it easier to do automated and production builds.


Documentation for latest development version:

Issues and support

ESP8266 Community Forum is a well established community for questions and answers about Arduino for ESP8266.

If you find this forum useful, please consider supporting it with a donation.

If you encounter an issue which you think is a bug in the ESP8266 Arduino Core or the associated libraries, you are welcome to submit it here on Github:

Please provide as much context as possible:

  • ESP8266 Arduino core version which you are using (you can check it in Boards Manager)
  • your sketch code; please wrap it into a code block, see Github markdown manual
  • when encountering an issue which happens at run time, attach serial output. Wrap it into a code block, just like the code.
  • for issues which happen at compile time, enable verbose compiler output in the IDE preferences, and attach that output (also inside a code block)
  • ESP8266 development board model
  • IDE settings (board choich, flash size)


For minor fixes of code and documentation, please go ahead and submit a pull request.

Check out the list of issues which are easy to fix — easy issues for 2.5.0. Working on them is a great way to move the project forward.

Larger changes (rewriting parts of existing code from scratch, adding new functions to the core, adding new libraries) should generally be discussed by opening an issue first.

Feature branches with lots of small commits (especially titled "oops", "fix typo", "forgot to add file", etc.) should be squashed before opening a pull request. At the same time, please refrain from putting multiple unrelated changes into a single pull request.

License and credits

Arduino IDE is developed and maintained by the Arduino team. The IDE is licensed under GPL.

ESP8266 core includes an xtensa gcc toolchain, which is also under GPL.

Esptool written by Christian Klippel is licensed under GPLv2, currently maintained by Ivan Grokhotkov:

Espressif SDK included in this build is under Espressif MIT License.

ESP8266 core files are licensed under LGPL.

SPI Flash File System (SPIFFS) written by Peter Andersson is used in this project. It is distributed under MIT license.

umm_malloc memory management library written by Ralph Hempel is used in this project. It is distributed under MIT license.

axTLS library written by Cameron Rich, built from, is used in this project. It is distributed under BSD license.