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Custom Features


Note: this page is now out of date, see updated functionality in the code (WLED/usermods/EXAMPLE_v2)

This page is intended for those wishing to modify the WLED code to add their own functionality.


Programming is done in the Arduino IDE. There is a special file, usermod.cpp, to write your own code. (however, if you think your code may be relevant to many users, feel free to code it in directly and open a pull request)

This file has three empty methods: - userSetup() is called after loading settings but before connecting to WiFi. Use it to start own interfaces if it does not depend on WiFi (IR, Sensors, GPIOs,...). Also you can use it to load custom settings or to specify own server pages with the server.on() method. - userConnected() is called once WiFi is connected. Use it to connect to external servers or init interfaces using wiFi. - userLoop() is called by the main loop() function.

Modify WLED values

If you know what you're doing, you may choose to change the value of any global variable declared in wled.h. However, for basic color and brightness changes, these are the most important:

Variable Name Type Purpose
bri byte (0-255) Master Brightness (0 is off, 255 is maximum)
col[0] byte (0-255) Red color value
col[1] byte (0-255) Green color value
col[2] byte (0-255) Blue color value
col[3] byte (0-255) White color value

After updating the color, you must call the colorUpdated(int) method. If you want to send a notification with the new color to other ESPs, use colorUpdated(NOTIFIER_CALL_MODE_DIRECT_CHANGE), otherwise colorUpdated(NOTIFIER_CALL_MODE_NO_NOTIFY).


If you'd just like a simple modification that requires timing (like sending a request every 2 seconds), please never use the delay() function in your userLoop()! It will block everything else and WLED will become unresponsive and effects won't work! Instead, try this instead:

long lastTime = 0;
int delayMs = 2000; //we want to do something every 2 seconds

void userLoop()
  if (millis()-lastTime > delayMs)
    lastTime = millis();
    //do something you want to do every 2 seconds

Internal Segments API

You can use Segments from your code to set different parts of the strip to different colors or effects.
This can be very useful for highly customized installations, clocks, ...

To set a segment, use strip.setSegment(id, start, stop);, where id is the segment ID, start is the first LED of the segment and stop is the LED after the last one in the segment.

To edit the configuration of a segment, use:

WS2812FX::Segment& seg = strip.getSegment(id);
//set color (i=0 is primary, i=1 secondary i=2 tertiary)
seg.colors[i] = ((myWhite << 24) | ((myRed&0xFF) << 16) | ((myGreen&0xFF) << 8) | ((myBlue&0xFF)));
//set effect config
seg.mode = myFxI;
seg.speed = mySpeed;
seg.intensity = myIntensity;
seg.palette = myPaletteId;
Keep in mind that this will not cause interface updates as of 0.8.6. For that, you still need to use colorUpdated(NOTIFIER_CALL_MODE_DIRECT_CHANGE)

Create ARTI-FX

It is possible to create your own effects and add them to the FX library. The relevant files for that are FX.cpp and FX.h.

Here is a step-by-step guide on how to make your effect:

  1. Take a look at some of the effects in FX.cpp to see how they are implemented!

  2. Add your own routine in FX.cpp starting with: uint16_t WS2812FX::mode_custom

  3. Add to total number of effects in FX.h line 110: #define MODE_COUNT

  4. Add your mode number (ie#define FX_MODE_CUSTOM 110) in FX.h around line 200.

  5. Add your mode around line 400 of FX.h, like so: _mode[FX_MODE_CUSTOM] = &WS2812FX::mode_custom;

  6. Add it to the functions in FX.h around line 600:mode_custom(void),

  7. Give it a name at the bottom (10 modes per line) in JSON_mode_names[]. Wrap your name in quotes just like the others.

  8. Compile, upload and enjoy! Your new effect will automatically be added to the list in the web ui.

If you programmed a nice effect you want to share, submit a pull request!

Create a custom effect as usermod

Since 0.14

This feature was introduced with version 0.14.

It is possible to add new effects in form of a usermod.

Use 255 for the effect ID as it is a placeholder for "1st available slot". If you want a permanent ID use whatever is not used by built-in effects or other usermod's effects. It is possible to call addEffect(255,...) multiple times to add more effects without a collision of IDs.

uint16_t mode_blink(void) {
  return FRAMETIME;

static const char _data_FX_MODE_BLINK[] PROGMEM = "Blink@!,Duty cycle;!,!;!;01";

class BlinkUsermod : public Usermod
    void setup()
      strip.addEffect(255, &mode_blink, _data_FX_MODE_BLINK);

    void loop()

    uint16_t getId()
      return USERMOD_ID_...;

For details about the format of the configuration string see effect metadata.

Changing Web UI

In order to conserve space, the Web UI interface is represented as a series of wled00/html_*.h files which contain C/C++ strings with specific parts of the Web UI.

These files are automatically created from source files available in wled00/data folder. To generate files, install Node.js 20 or higher globally. After that, recreate html_*.h files by running in the repo directory:

> npm install
> npm run build

If you want to test changes to the UI, it is easiest to work with the local wled00/data/index.htm file. You just need to enter the IP address of a WLED 0.10.0 or newer instance into the popup. If you accidentally input an incorrect IP or want to test with a different instance, clear the local storage (in Chrome: Developer Tools -> Application -> Local Storage)

If you continuously modify files in the wled00/data directory, you want to monitor these changes to make local html_*.h files being updated automatically. To do this, run this in repo directory:

> npm run dev
This will start monitoring wled00/data folder for changes. However, you will probably never need this, as npm run build is automatically executed before compiling.

The html_*.h files will only be created or updated if changes have been made to the wled00/data folder. If you still want to recreate the files, you can use this command:

> npm run build -- -f

WARNING!! Be careful with changing the javascript in HTML files! For example function GetV() {} must be the last javascript function in the <script> element as it will be replaced by automatically generated code to fetch relevant settings from EEPROM. See tools/cdata.js for the replacement rules which run for every *.htm file in wled00/data.

Recompile and flash WLED!