Pa11y

Pa11y is your automated accessibility testing pal. It runs HTML CodeSniffer from the command line for programmatic accessibility reporting.

On the command line:

pa11y nature.com

In JavaScript:

var pa11y = require('pa11y');

var test = pa11y(options);

test.run('nature.com', function (error, results) {
    /* ... */
});

✨ 🔜 ✨ The Pa11y team is very excited to announce plans for the successor to Pa11y Dashboard and Pa11y Webservice, codename "Sidekick". Help us define the features that you want to see by visiting the proposal. ✨

Requirements
Command-Line Interface
JavaScript Interface
Configuration
Examples
Common Questions
Contributing
Support and Migration
License

Requirements

Pa11y requires Node.js 4+ to run.

OS X

On a Mac, you can install the required dependency with Homebrew:

$ brew install node

Alternatively download pre-built packages from the Node.js website.

Linux

Depending on your flavour of Linux, you should be able to use a package manager to install the required dependency. Alternatively download pre-built packages from the Node.js website.

Windows

Windows users approach with caution – we've been able to get Pa11y running (Windows 7, Node 4) but only after installing Visual Studio and the Windows SDK (as well as Git, and Python). The Windows installation instructions for node-gyp are a good place to start.

Command-Line Interface

Install Pa11y globally with npm:

npm install -g pa11y

This installs the pa11y command-line tool:

Usage: pa11y [options] <url>

  Options:

    -h, --help                    output usage information
    -V, --version                 output the version number
    -s, --standard <name>         the accessibility standard to use: Section508, WCAG2A, WCAG2AA (default), WCAG2AAA
    -r, --reporter <reporter>     the reporter to use: cli (default), csv, html, json
    -l, --level <level>           the level of message to fail on (exit with code 2): error, warning, notice
    -T, --threshold <number>        permit this number of errors, warnings, or notices, otherwise fail with exit code 2
    -i, --ignore <ignore>         types and codes of messages to ignore, a repeatable value or separated by semi-colons
    -E, --hide-elements <hide>    a CSS selector to hide elements from testing, selectors can be comma separated
    -R, --root-element <element>  the root element for testing a subset of the document
    -c, --config <path>           a JSON or JavaScript config file
    -p, --port <port>             the port to run PhantomJS on
    -t, --timeout <ms>            the timeout in milliseconds
    -w, --wait <ms>               the time to wait before running tests in milliseconds
    -v, --verify-page <string>    HTML string to verify is present in the page source HTML
    -d, --debug                   output debug messages
    -H, --htmlcs <url>            the URL or path to source HTML_CodeSniffer from
    -e, --phantomjs <path>        the path to the phantomjs executable

Running Tests

Run an accessibility test against a URL:

pa11y http://nature.com

Run an accessibility test against a file (absolute paths only, not relative):

pa11y file:///path/to/your/file.html

Run a test with CSV reporting and save to a file:

pa11y --reporter csv http://nature.com > report.csv

Run Pa11y with the Section508 ruleset:

pa11y --standard Section508 http://nature.com

Exit Codes

The command-line tool uses the following exit codes:

0: Pa11y ran successfully, and there are no errors
1: Pa11y failed run due to a technical fault
2: Pa11y ran successfully but there are errors in the page

By default, only accessibility issues with a type of error will exit with a code of 2. This is configurable with the --level flag which can be set to one of the following:

error: exit with a code of 2 on errors only, exit with a code of 0 on warnings and notices
warning: exit with a code of 2 on errors and warnings, exit with a code of 0 on notices
notice: exit with a code of 2 on errors, warnings, and notices
none: always exit with a code of 0

Command-Line Configuration

The command-line tool can be configured with a JSON file as well as arguments. By default it will look for a pa11y.json file in the current directory, but you can change this with the --config flag:

pa11y --config ./path/to/config.json http://nature.com

For more information on configuring Pa11y, see the configuration documentation.

Ignoring

The ignore flag can be used in several different ways. Separated by semi-colons:

pa11y --ignore "warning;notice" http://nature.com

or by using the flag multiple times:

pa11y --ignore warning --ignore notice http://nature.com

Pa11y can also ignore notices, warnings, and errors up to a threshold number. This might be useful if you're using CI and don't want to break your build. The following example will return exit code 0 on a page with 9 errors, and return exit code 2 on a page with 11 errors.

pa11y --threshold 10 http://nature.com

Reporters

The command-line tool can report test results in a few different ways using the --reporter flag. The built-in reporters are:

cli: output test results in a human-readable format
csv: output test results as comma-separated values
html: output test results as an HTML document
json: output test results as a JSON array
markdown: output test results as a Markdown document

You can also write and publish your own reporters. Pa11y looks for reporters in the core library, your node_modules folder (with a naming pattern), and the current working directory. The first reporter found will be loaded. So with this command:

pa11y --reporter rainbows http://nature.com

The following locations will be checked:

<pa11y-core>/reporter/rainbows
<cwd>/node_modules/pa11y-reporter-rainbows
<cwd>/rainbows

A Pa11y reporter should export the following methods, and these should make use of console to send output:

begin(url); // Called when pa11y starts
error(message); // Called when a technical error is reported
debug(message); // Called when a debug message is reported
info(message); // Called when an information message is reported
results(resultsArray, url); // Called with the results of a test run

Reporters may also optionally export a process method. This should accept the same arguments as the results method but return the processed results rather than outputting them:

process(resultsArray, url); // Called with results by a user

You may find the following reporters useful:

1.0-json: output test results in the Pa11y 1.0 JSON format

JavaScript Interface

Install Pa11y with npm or add to your package.json:

npm install pa11y

Require Pa11y:

var pa11y = require('pa11y');

Create a tester by initialising Pa11y with some options:

var test = pa11y(options);

The test.run function can then be used to run your test function against a URL:

test.run('http://www.nature.com/', function(error, results) {
    // ...
});

The results that get passed into your test callback come from HTML CodeSniffer, and look like this:

[
    {
        code: 'WCAG2AA.Principle1.Guideline1_1.1_1_1.H30.2',
        context: '<a href="http://example.com/"><img src="example.jpg" alt=""/></a>',
        message: 'Img element is the only content of the link, but is missing alt text. The alt text should describe the purpose of the link.',
        selector: 'html > body > p:nth-child(1) > a',
        type: 'error',
        typeCode: 1
    },
    {
        code: 'WCAG2AA.Principle1.Guideline1_3.1_3_1.H49.B',
        context: '<b>Hello World!</b>',
        message: 'Semantic markup should be used to mark emphasised or special text so that it can be programmatically determined.',
        selector: '#content > b:nth-child(4)',
        type: 'warning',
        typeCode: 2
    },
    {
        code: 'WCAG2AA.Principle2.Guideline2_4.2_4_4.H77,H78,H79,H80,H81',
        context: '<a href="http://example.com/">Hello World!</a>',
        message: 'Check that the link text combined with programmatically determined link context identifies the purpose of the link.',
        selector: 'html > body > ul > li:nth-child(2) > a',
        type: 'notice',
        typeCode: 3
    }
]

If you wish to transform these results with the command-line reporters, then you can do so in your code by requiring them in. The csv, html, json, and markdown reporters all expose a process method:

// Assuming you've already run tests, and the results
// are available in a `results` variable:
var htmlReporter = require('pa11y/reporter/html');
var html = htmlReporter.process(results, url);

Configuration

Pa11y has lots of options you can use to change the way PhantomJS runs, or the way your page is loaded. Options can be set either on the Pa11y instance when it's created or the individual test runs. This allows you to set some defaults which can be overridden per-test:

// Set the default Foo header to "bar"
var test = pa11y({
    page: {
        headers: {
            Foo: 'bar'
        }
    }
});

// Run a test with the Foo header set to "bar"
test.run('http://www.nature.com/', function(error, results) { /* ... */ });

// Run a test with the Foo header overridden
test.run('http://www.nature.com/', {
    page: {
        headers: {
            Foo: 'hello'
        }
    }
}, function(error, results) { /* ... */ });

Below is a reference of all the options that are available:

`allowedStandards` (array)

The accessibility standards that are allowed to be used. This can be modified to allow for custom HTML CodeSniffer standards.

pa11y({
    allowedStandards: ['WCAG2AA', 'My Custom Standard']
});

Defaults to Section508, WCAG2A, WCAG2AA, and WCAG2AAA.

`beforeScript` (function)

A function to be run before Pa11y tests the page. The function accepts three parameters;

page is the phantomjs page object, documentation for the phantom bridge can be found here
options is the finished options object used to configure pa11y
next is a callback function

pa11y({
    beforeScript: function(page, options, next) {
		// Make changes to the page
		// When finished call next to continue running Pa11y tests
		next();
	}
});

Defaults to null.

`hideElements` (string)

A CSS selector to hide elements from testing, selectors can be comma separated. Elements matching this selector will be hidden from testing by styling them with visibility:hidden.

pa11y({
	hideElements: '.advert, #modal, div[aria-role=presentation]'
});

`htmlcs` (string)

The path or URL to source HTML CodeSniffer from.

pa11y({
    htmlcs: 'http://squizlabs.github.io/HTML_CodeSniffer/build/HTMLCS.js'
});

Defaults to a local copy of HTML CodeSniffer, found in lib/vendor/HTMLCS.js.

`ignore` (array)

An array of result codes and types that you'd like to ignore. You can find the codes for each rule in the console output and the types are error, warning, and notice.

pa11y({
    ignore: [
        'notice',
        'WCAG2AA.Principle3.Guideline3_1.3_1_1.H57.2'
    ]
});

Defaults to an empty array.

`log` (object)

An object which implements the methods debug, error, and info which will be used to report errors and test information.

pa11y({
    log: {
        debug: console.log.bind(console),
        error: console.error.bind(console),
        info: console.info.bind(console)
    }
});

Each of these defaults to an empty function.

`page.headers` (object)

A key-value map of request headers to send when testing a web page.

pa11y({
    page: {
        headers: {
            Cookie: 'foo=bar'
        }
    }
});

Defaults to an empty object.

`page.settings` (object)

A key-value map of settings to add to the PhantomJS page. For a full list of available settings, see the PhantomJS page settings documentation.

pa11y({
    page: {
        settings: {
            loadImages: false,
            userName: 'nature',
            password: 'say the magic word'
        }
    }
});

Defaults to:

{
    userAgent: 'pa11y/<version> (truffler/<version>)'
}

`page.viewport` (object)

The viewport width and height in pixels. The viewport object must have both width and height properties.

pa11y({
    page: {
        viewport: {
            width: 320,
            height: 480
        }
    }
});

Defaults to:

{
    width: 1024,
    height: 768
}

`phantom` (object)

A key-value map of settings to initialise PhantomJS with. This is passed directly into the phantom module – documentation can be found here. You can pass PhantomJS command-line parameters in the phantom.parameters option as key-value pairs.

pa11y({
    phantom: {
        port: 1234,
        parameters: {
            'ignore-ssl-errors': 'false',
            'ssl-protocol': 'tlsv1'
        }
    }
});

Defaults to:

{
    parameters: {
        'ignore-ssl-errors': 'true'
    }
}

If phantom.port is not specified, a random available port will be used.

`rootElement` (element)

The root element for testing a subset of the page opposed to the full document.

pa11y({
    rootElement: '#main'
});

Defaults to null, meaning the full document will be tested.

`standard` (string)

The accessibility standard to use when testing pages. This should be one of Section508, WCAG2A, WCAG2AA, or WCAG2AAA (or match one of the standards in the allowedStandards option).

pa11y({
    standard: 'Section508'
});

Defaults to WCAG2AA.

`timeout` (number)

The time in milliseconds that a test should be allowed to run before calling back with a timeout error.

pa11y({
    timeout: 500
});

Defaults to 30000.

`wait` (number)

The time in milliseconds to wait before running HTML CodeSniffer on the page.

pa11y({
    wait: 500
});

Defaults to 0.

`verifyPage` (string)

HTML string to verify is present in the page source HTML. Could be used to ascertain that intended page is being tested (as opposed to error page) by using <title> tags and content (as below), or that a specific element is present.

pa11y({
    verifyPage: '<title>Nature Research: science journals, jobs, information and services.</title>'
});

Defaults to null.

Examples

Basic Example

Run Pa11y on a URL and output the results. See the example, or run it with:

node example/basic

Multiple Example

Use async to run Pa11y on multiple URLs in series, and output the results. See the example, or run it with:

node example/multiple

Multiple Concurrent Example

Use async to run Pa11y on multiple URLs in parallel, with a configurable concurrency. Then output the results. See the example, or run it with:

node example/multiple-concurrent

Before Script Example

Inject a script before Pa11y runs. This example logs into a fictional site then waits until the account page has loaded before running Pa11y. See the example.

Common Questions

Common questions about Pa11y are answered here.

How do I set cookies on a tested page?

Use the page.headers option either in your JS code or in your config file:

pa11y({
    page: {
        headers: {
            Cookie: 'foo=bar'
        }
    }
});

How can Pa11y log in if my site's behind basic auth?

Use the page.settings option either in your JS code or in your config file to set a username and password:

pa11y({
    page: {
        settings: {
            userName: 'nature',
            password: 'say the magic word'
        }
    }
});

How can Pa11y log in if my site has a log in form?

Use the beforeScript option either in your JS code or in your config file to input login details and submit the form. Once the form has been submitted you will also have to wait until the page you want to test has loaded before calling next to run Pa11y.

pa11y({
	beforeScript: function(page, options, next) {
		var waitUntil = function(condition, retries, waitOver) {
			page.evaluate(condition, function(error, result) {
				if (result || retries < 1) {
					waitOver();
				} else {
					retries -= 1;
					setTimeout(function() {
						waitUntil(condition, retries, waitOver);
					}, 200);
				}
			});
		};

		page.evaluate(function() {
			var user = document.querySelector('#username');
			var password = document.querySelector('#password');
			var submit = document.querySelector('#submit');

			user.value = 'exampleUser';
			password.value = 'password1234';

			submit.click();

		}, function() {

			waitUntil(function() {
				return window.location.href === 'http://example.com/myaccount';
			}, 20, next);
		});
	}
});

How can I use Pa11y with a proxy server?

Use the phantom.parameters option either in your JS code or in your config file:

pa11y({
    phantom: {
        parameters: {
            'proxy': '1.2.3.4:8080',
            'proxy-type': 'http',
            'proxy-auth': 'username:password'
        }
    }
});

These match PhantomJS command-line parameters. proxy-type can be set to http, socks5, or none.

How can I simulate a user interaction before running Pa11y?

Use the beforeScript option either in your JS code or in your config file to simulate the interactions before running Pa11y.

In this example, additional content is loaded via ajax when a button is clicked. Once the content is loaded the aria-hidden attribute switches from true to false.

pa11y({
	beforeScript: function(page, options, next) {
		var waitUntil = function(condition, retries, waitOver) {
			page.evaluate(condition, function(error, result) {
				if (result || retries < 1) {
					waitOver();
				} else {
					retries -= 1;
					setTimeout(function() {
						waitUntil(condition, retries, waitOver);
					}, 200);
				}
			});
		};

		page.evaluate(function() {
			var ajaxButton = document.querySelector('#loadContent');
			var dynamicContent = document.querySelector('#content');

			ajaxButton.click();

		}, function() {

			waitUntil(function() {
				return dynamicContent.getAttribute('aria-hidden') === 'false';
			}, 20, next);
		});
	}
});

Why does Pa11y give different results to HTML CodeSniffer bookmarklet ?

Pa11y uses PhantomJS as a headless web browser to load the DOM content and can only analyze what is provided. If parts of the DOM are been loaded after the document is first generated, you may get results that differ from the bookmarklet which runs in the browser and can test against the complete DOM.

If you use Pa11y and HTML CodeSniffer CLI you will find that you get the same results, which will both differ from the bookmarklet, a similar issue was highlighted by HTML CodeSniffer.

We are aware of an issue with regard to iframe content, PhantomJS doesn't automatically provide access to the inner content of iframes, and so Pa11y doesn't currently support testing against iframe content from a parent page context. Any page that makes use of iframes, e.g. for displaying ads, may show different results on Pa11y than those when running HTML_CodeSniffer in the browser.

If you do need to test the contents of an iframe, run Pa11y against the iframe source URL directly.

Is Pa11y testing the contrast of the hover state ?

Pa11y doesn't check the hover state. Instead, you must test the contrast of the hover state for links manually.

Contributing

There are many ways to contribute to Pa11y, we cover these in the contributing guide for this repo.

If you're ready to contribute some code, clone this repo locally and commit on a separate branch. Please write unit tests for your changes, and check that everything works by running the following before opening a pull-request:

make ci

Support and Migration

Pa11y major versions are normally supported for 6 months after their last minor release. This means that patch-level changes will be added and bugs will be fixed. The table below outlines the end-of-support dates for major versions, and the last minor release for that version.

We also maintain a migration guide to help you migrate.

❔	Major Version	Last Minor Release	Node.js Versions	Support End Date
❤️	4	N/A	4+	N/A
⌛	3	3.8	0.12–6	2016-12-05
💀	2	2.4	0.10–0.12	2016-10-16
💀	1	1.7	0.10	2016-06-08

If you're opening issues related to these, please mention the version that the issue relates to.

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