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) {
/* ... */
});
- Requirements
- Command-Line Interface
- JavaScript Interface
- Configuration
- Examples
- Common Questions
- Contributing
- Migrating
- License
pa11y requires Node.js 0.12+ and PhantomJS to run.
On a Mac, you can install these with Homebrew:
$ brew install node
$ brew install phantomjs
If you're on Linux, you'll probably be able to work it out.
Windows users approach with caution – we've been able to get pa11y running (Windows 7, Node 0.12) but only after installing Visual Studio and the Windows SDK (as well as Git, Python and PhantomJS). The Windows installation instructions for node-gyp are a good place to start.
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 <name> the number of errors to permit before failing
-i, --ignore <ignore> types and codes of messages to ignore separated by semi-colons
-c, --config <path> a JSON 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
-d, --debug output debug messages
-H, --htmlcs <url/path> the URL or path to source HTML_CodeSniffer from
-e, --phantomjs <path> the path to the phantomjs executable
Run an accessibility test against a URL:
pa11y nature.com
Run a test with CSV reporting and save to a file:
pa11y --reporter csv nature.com > report.csv
Run pa11y with the Section508 ruleset:
pa11y --standard Section508 nature.com
The command-line tool uses the following exit codes:
0
: pa11y ran successfully, and there are no errors1
: pa11y failed run due to a technical fault2
: 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 of2
on errors only, exit with a code of0
on warnings and noticeswarning
: exit with a code of2
on errors and warnings, exit with a code of0
on noticesnotice
: exit with a code of2
on errors, warnings, and noticesnone
: always exit with a code of0
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 nature.com
For more information on configuring pa11y, see the configuration documentation.
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 formatcsv
: output test results as comma-separated valueshtml
: output test results as an HTML documentjson
: output test results as a JSON arraymarkdown
: 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 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:
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
You may find the following reporters useful:
1.0-json
: output test results in the pa11y 1.0 JSON format
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
}
]
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:
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.
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.
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.
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.
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>)'
}
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
}
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.
The accessibility standard to use when testing pages. This should be one of Section508
, WCAG2A
, WCAG2AA
, or WCAG2AAA
.
pa11y({
standard: 'Section508'
});
Defaults to WCAG2AA
.
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
.
The time in milliseconds to wait before running HTML CodeSniffer on the page.
pa11y({
wait: 500
});
Defaults to 0
.
Run pa11y on a URL and output the results:
node example/basic
Use async to run pa11y on multiple URLs in series, and output the results:
node example/multiple
Common questions about pa11y are answered here.
Use the page.headers
option either in your JS code or in your JSON config file:
pa11y({
page: {
headers: {
Cookie: 'foo=bar'
}
}
});
Use the page.settings
option either in your JS code or in your JSON config file to set a username and password:
pa11y({
page: {
settings: {
userName: 'nature',
password: 'say the magic word'
}
}
});
Use the phantom.parameters
option either in your JS code or in your JSON 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
.
To contribute to pa11y, clone this repo locally and commit your code on a separate branch.
Please write unit tests for your code, and check that everything works by running the following before opening a pull-request:
make ci
If you're using pa11y 1.0 or 2.0 and wish to migrate to 3.0, we've written a Migration Guide to help with that.
It's recommended that you migrate to 3.0 as soon as possible, but we maintain branches for previous major versions. Each of these will be supported (critical bug fixes only) for 1 year from the next major version's released date:
If you're opening issues related to these, please mention the version being used.
Copyright 2013 Nature Publishing Group.
pa11y is licensed under the GNU General Public License 3.0.