In Espruino, Modules are pieces of pre-written code that perform common tasks, such as interfacing to different bits of hardware. On this site we generally mean the same thing when referring to "modules" or "libraries".

They can either be JS modules that are loaded from the internet on demand, or they may come compiled in to the Espruino firmware itself.

Working with Modules

Note: Module names are case sensitive. For example require("WiFi") and require("Wifi") do not do the same thing.

If you're using the Espruino Web IDE or Espruino command-line tools, simply write require("modulename") on the right-hand side. When you click the Send to Espruino button, the Web IDE (or command line tools) will automatically look online for minified versions of the modules you need, download them, and load them onto the board. You don't need an SD card or an internet connection to the Espruino board itself.

Note: The left-hand side of the IDE is a direct connection to the board itself, which the IDE does not interfere with. As such, if you type require("modulename") in the left-hand side then the IDE will not have a chance to dynamically load the module for you, so if it's not in Espruino you won't be able to use it. To fix that, just add require("modulename") to the right-hand side of the IDE (nothing else is required) and click Send to Espruino - the IDE will then upload that module and you'll be able to use it from the left-hand side.

Built-in modules

Some modules come built-in to the Espruino firmware on certain boards. If this is the case then the Web IDE won't attempt to load the module and the built-in one will be used.

You can check which modules your board has just connecting to it with the Web IDE, then clicking the Settings icon in the Web IDE, going to Board Information and looking at MODULES (the same info is available by typing process.env.MODULES too).

You can find more information on most of them via Espruino's Software Reference

If the Web IDE says Module not found when trying to upload a module that you know exists on your board, try reconnecting the IDE. If the IDE fails to communicate with the board when it first connects, it will be unable to get a list of the preinstalled modules and so will assume the module has to be downloaded (many pre-installed modules do not have downloadable equivalents).

Espruino Modules

If you are using the Web IDE or command-line tools as is, the modules will be loaded from (which is a curated set of modules in This URL can be changed in Web IDE settings.

To save space, most modules are provided as a minified version and the Web IDE tries to load minified versions first with default configuration (this can be changed in Settings -> Communications -> Module Extensions).

For example, using require("ADNS5050"); will make the Web IDE load the minified module from

If you need to use modules while not connected to the internet, Settings -> Offline Mode allows you to download all available modules for offline use.

from Github (or anywhere on the internet)

You can type a URL into require, so you can actually just pull a module right off GitHub:


You can even look at the history of something on GitHub, and can then require a specific version of that file with:


The URL comes from clicking <> by the commit you were interested in in GitHub.

Note: You can use any URL, however because the Web IDE runs in a browser, the server that you access files from must have Cross Origin Resource Sharing (CORS) headers enabled.

from Storage

On Espruino 2v00 and above on devices with enough memory you can write a module to Espruino's flash memory using the built-in Storage module. It'll then be loaded automatically by Espruino:

exports.get = function() {
  return 42;
// prints 42


from NPM

There was a beta option in Web IDE to load modules from the NPM repository. After some testing it was removed (The vast majority of NPM modules are just too large to fit in a microcontroller with their dependencies).

If you require NPM modules we'd recommend that you use a tree-shaking/bundling system like rollup to bundle your NPM modules into one file, and then use the Espruino command-line tools to upload it.

from a local folder

If you set a project folder with Web IDE -> Settings -> Project, the Web IDE will automatically create an empty modules folder inside it. Put a module there and you can load it with require("myCustomModule");.

Note: This feature is not currently implemented in the 'Web App' IDE available at You'll need to use the Native versions

With default Web IDE configuration, it will look for modules following this order:

  1. local minified
  2. online minified
  3. local normal
  4. online normal

If your own module has the same name as one of the existing ones, the Web IDE will use the minified version from online first.

If you need it anyway, you can provide a local minified version or you can change the Web IDE configuration from .min.js|.js to .js|.min.js or even myCustomModule.js|.min.js|.js to get it working.

Note: When the Web IDE is running in the browser it cannot access any folders on your local computer, so the Projects functionality is disabled.

from SD card

If you have an Espruino with an SD card (but you're not using the Web IDE), you can copy the modules you need into a directory called 'node_modules' on the SD card. Now, whenever you write require("modulename") the module will be used.

If you don't have an SD card, see Modules from Storage above.

from the Internet

The Web IDE or command-line tools will load modules from the internet automatically when you upload - see Espruino modules above.

However an Internet-connected Espruino device can't automatically load a modules from the internet by itself because require is synchronous while network connections are asynchronous.

However you can use the following asyncronous code to load a module from the internet on demand.

function loadModule(moduleName, callback) {
  require("http").get(""+moduleName+".min.js", function(res) {
    var contents = "";
    res.on('data', function(data) { contents += data; });
    res.on('close', function() {
      Modules.addCached(moduleName, contents);
      if (callback) callback();
  }).on('error', function(e) {
    console.log("ERROR", e);

// for example:
loadModule("PCD8544", function() { // loads PCD8544.min.js
  SPI1.setup({ sck:B3, mosi:B5 });
  var g = require("PCD8544").connect(SPI1, B6 /*DC*/, B7 /*CE*/, B8 /*RST*/, function() {

Existing Modules

These are the existing modules that are available for download to Espruino:

Built-in Functionality

Espruino also contains many built-in modules and classes that provide a lot of functionality - these are some of them:

You don't need a module to be able to interface to hardware - sometimes it just makes it easier. If you want to interface to a device that isn't listed here, please check out the Tutorials page, or Search for it.

Frequently Asked Questions

Why don't modules work when typing require on the left-hand side of the Web IDE (or from a terminal window)?

When you type require("modulename") on the right-hand side and click Send to Espruino, the Espruino Web IDE scans your code for require statements and loads the relevant modules off the internet. Because the left-hand side of the Web IDE (or a terminal window) sends each character direct to Espruino, by the time you have pressed enter to execute your command, it's then too late to load the module.

Instead, Espruino defaults to what is mentioned under the Stand-alone Espruino heading above - it looks on an SD card (if inserted) for the module. This is why you might get a ERROR: Unable to read file : NOT_READY error written to the console.

If I load modules from an SD card, will the SD card always need to be inserted?

No. As long as you have used require('module') at least once for each module before you type save(), all the information that is needed will be cached inside Espruino.

Can I dynamically load (and unload) modules?

Yes. By default each module that is loaded will be cached (to avoid loading modules twice). However you can call Modules.removeCached('modulename') which will remove the module from the cache and free the memory that it uses.

How do I make my own modules?

It's easy! See the Writing Modules page...

This page is auto-generated from GitHub. If you see any mistakes or have suggestions, please let us know.