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Contributor License Agreement

In order to contribute, you must accept the contributor license agreement (CLA). Acceptance of this agreement will be checked automatically and pull requests without a CLA cannot be merged.

Contribution Guidelines

Submitting code to the project? Please review and follow our Git commit and pull request guidelines.

Code Quality

Although we do not have official code style guidelines, we can and will request you to make changes if we think that your code is sloppy. You can take clues from the existing code base to see what we consider to be reasonable code quality. Please be prepared to make changes that we ask of you even if you might not agree with the request(s).

Please respect the coding style of the files you are changing and adhere to that.

The JavaScript files in this project are formatted by Prettier. Additionally, we prefer:

  1. Tabs over spaces
  2. Single quotes for string literals
  3. Function definitions like function functionName(arguments) {
  4. Variable function definitions like Class.prototype.functionName = function (arguments) {
  5. Use of 'use strict'
  6. Variables declared at the top of functions

Shadow DOM

For any proposed changes to rules, checks, commons, or other APIs to be accepted in axe-core, your code must support open Shadow DOM. See and the developer guide for documentation on the available methods and test utilities. You can also look at existing tests for examples using our APIs.


We expect all code to be 100% covered by tests. We don't have or want code coverage metrics but we will review tests and suggest changes when we think the test(s) do(es) not adequately exercise the code/code changes.

Documentation and Comments

Functions should contain a preceding comment block with jsdoc style documentation of the function. For example:

 * Runs the Audit; which in turn should call `run` on each rule.
 * @async
 * @param  {Context}   context The scope definition/context for analysis (include/exclude)
 * @param  {Object}    options Options object to pass into rules and/or disable rules or checks
 * @param  {Function} fn       Callback function to fire when audit is complete

Classes should contain a jsdoc comment block for each attribute. For example:

 * Constructor for the result of checks
 * @param {Object} check CheckResult specification
function CheckResult(check) {
	'use strict';

	 * ID of the check.  Unique in the context of a rule.
	 * @type {String}
	 */ =;

	 * Any data passed by Check (by calling ``)
	 * @type {Mixed}
	 */ = null;

	 * Any node that is related to the Check, specified by calling `this.relatedNodes([HTMLElement...])` inside the Check
	 * @type {Array}
	this.relatedNodes = [];

	 * The return value of the Check's evaluate function
	 * @type {Mixed}
	this.result = null;

Setting up your environment

In order to get going, fork and clone the repository. Then, if you do not have Node.js installed, install it!

Once the basic infrastructure is installed, from the repository root, do the following:

npm install

To run tests:

grunt test

To build the package:

grunt build

Using axe with TypeScript

Axe Development

The TypeScript definition file for axe-core is distributed with this module and can be found in axe.d.ts. It currently supports TypeScript 2.0+.

To maintain axe support for TypeScript you must first install it (globally recommended):

sudo npm -g install typescript

Once that's installed, you can run TypeScript definition tests (with the optional --noImplicitAny flag):

tsc --noImplicitAny typings/axe-core/axe-core-tests.ts

Including axe's type definition in tests

Installing axe to run accessibility tests in your TypeScript project should be as simple as importing the module:

import * as axe from 'axe-core';

describe('Module', () => {
	it('should have no accessibility violations', done => { => {
		}, done);

Debugging tests that only fail on CircleCI

First install an X-Windows client on your machine. XQuartz is a good one.

Then follow the instructions here to connect the X-Windows on CircleCI to XQuartz

Start the build using the "Retry the build with SSH enabled" option in the CircleCI interface

Copy the SSH command and add the -X flag to it for example

ssh -X -p 64605 ubuntu@

When you login, set up the environment and start the chrome browser

export DISPLAY=localhost:10.0

.Xauthority does not exist

Edit the ~/.Xauthority file and just save it with the following commands

vi ~/.Xauthority

Starting the web server

Log into a second ssh terminal (without -X) and execute the following commands

cd axe-core
grunt connect watch

Load your test file URL in the Chrome browser opened in XQuartz

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