@storybook/addon-a11y

What is @storybook/addon-a11y?

The @storybook/addon-a11y package is an addon for Storybook that helps you improve the accessibility of your UI components. It integrates with Storybook to provide automated checks and manual testing tools for accessibility issues, allowing developers to ensure their components are accessible to as many users as possible.

What are @storybook/addon-a11y's main functionalities?

Automated accessibility checks

Automatically run accessibility checks on your components within the Storybook UI. It uses the axe-core library to test each component for accessibility issues and provides a report.

import { withA11y } from '@storybook/addon-a11y';

export default {
  title: 'Button',
  decorators: [withA11y],
};

export const AccessibleButton = () => <button>Click me</button>;
export const InAccessibleButton = () => <button style={{ color: 'white', backgroundColor: 'white' }}>Can't see me</button>;

Manual accessibility testing tools

Provides tools for manual accessibility testing, such as color contrast checkers and keyboard event simulation, to complement the automated checks.

N/A

Customizable rules

Allows customization of the accessibility rules used for testing, enabling or disabling specific rules to tailor the checks to your project's needs.

import { withA11y } from '@storybook/addon-a11y';

export default {
  title: 'Button',
  decorators: [withA11y],
  parameters: {
    a11y: {
      config: {
        rules: [{ id: 'color-contrast', enabled: false }]
      }
    }
  }
};

Other packages similar to @storybook/addon-a11y

axe-core

A core library for accessibility testing used by many tools and services, including @storybook/addon-a11y. It can be integrated directly into testing workflows or used as part of other tools.

eslint-plugin-jsx-a11y

An ESLint plugin that enforces accessibility rules in JSX elements. Unlike @storybook/addon-a11y, which is used within Storybook, this plugin integrates with the ESLint static code analysis tool to catch accessibility issues during code linting.

react-axe

A library that can be used in React applications to audit accessibility in real-time during development. It also uses axe-core under the hood but is used directly in the app rather than in Storybook.

pa11y

An automated accessibility testing tool that runs in the command line or as part of your build process. It provides a different approach to accessibility testing compared to the Storybook addon, as it can be used for testing entire pages and is not specific to a component development environment.

README

storybook-addon-a11y

This Storybook addon can be helpful to make your UI components more accessible.

Framework Support

Getting started

First, install the addon.

$ yarn add @storybook/addon-a11y --dev

Add this line to your main.js file (create this file inside your Storybook config directory if needed).

export default {
  addons: ['@storybook/addon-a11y'],
};

And here's a sample story file to test the addon:

import React from 'react';

export default {
  title: 'button',
};

export const Accessible = () => <button>Accessible button</button>;

export const Inaccessible = () => (
  <button style={{ backgroundColor: 'red', color: 'darkRed' }}>Inaccessible button</button>
);

Handling failing rules

When Axe reports accessibility violations in stories, there are multiple ways to handle these failures depending on your needs.

Story-level overrides

At the Story level, override rules using parameters.a11y.config.rules.

export const InputWithoutAutofill = () => <input type="text" autocomplete="nope" />;

InputWithoutAutofill.parameters = {
  a11y: {
    // Avoid doing this, as it will fully disable all accessibility checks for this story.
    disable: true,

    // Instead, override rules 👇
    // axe-core configurationOptions (https://github.com/dequelabs/axe-core/blob/develop/doc/API.md#parameters-1)
    config: {
      rules: [
        {
          // You can exclude some elements from failing a specific rule:
          id: 'autocomplete-valid',
          selector: '*:not([autocomplete="nope"])',
        },
        {
          // You can also signify that a violation will need to be fixed in the future
          // by overriding the result of a rule to return "Needs Review"
          // rather than "Violation" if the rule fails:
          id: 'landmark-complementary-is-top-level',
          reviewOnFail: true,
        },
      ],
    },
  },
};

Alternatively, you can disable specific rules in a Story:

export const Inaccessible = () => (
  <button style={{ backgroundColor: 'red', color: 'darkRed' }}>Inaccessible button</button>
);
Inaccessible.parameters = {
  a11y: {
    config: {
      rules: [{ id: 'color-contrast', enabled: false }],
    },
  },
};

Tip: clearly explain in a comment why a rule was overridden, it’ll help you and your team trace back why certain violations aren’t being reported or need to be addressed. For example:

MyStory.parameters = {
  a11y: {
    config: {
      rules: [
        {
          // Allow `autocomplete="nope"` on form elements,
          // a workaround to disable autofill in Chrome.
          // @link https://bugs.chromium.org/p/chromium/issues/detail?id=468153
          id: 'autocomplete-valid',
          selector: '*:not([autocomplete="nope"])',
        },
        {
          // @fixme Color contrast of subdued text fails, as raised in issue #123.
          id: 'color-contrast',
          reviewOnFail: true,
        },
      ],
    },
  },
};

Global overrides

When you want to ignore an accessibility rule or change its settings across all stories, set parameters.a11y.config.rules in your Storybook’s preview.ts file. This can be particularly useful for ignoring false positives commonly reported by Axe.

// .storybook/preview.ts

export const parameters = {
  a11y: {
    config: {
      rules: [
        {
          // This tells Axe to run the 'autocomplete-valid' rule on selectors
          // that match '*:not([autocomplete="nope"])' (all elements except [autocomplete="nope"]).
          // This is the safest way of ignoring a violation across all stories,
          // as Axe will only ignore very specific elements and keep reporting
          // violations on other elements of this rule.
          id: 'autocomplete-valid',
          selector: '*:not([autocomplete="nope"])',
        },
        {
          // To disable a rule across all stories, set `enabled` to `false`.
          // Use with caution: all violations of this rule will be ignored!
          id: 'autocomplete-valid',
          enabled: false,
        },
      ],
    },
  },
};

Disabling checks

If you wish to entirely disable a11y checks for a subset of stories, you can control this with story parameters:

export const MyNonCheckedStory = () => <SomeComponent />;
MyNonCheckedStory.parameters = {
  // Avoid doing this, as it fully disables all accessibility checks for this story,
  // and consider the techniques described above.
  a11y: { disable: true },
};

Parameters

For more customizability use parameters to configure aXe options. You can override these options at story level too.

import React from 'react';
import { addDecorator, addParameters, storiesOf } from '@storybook/react';

export default {
  title: 'button',
  parameters: {
    a11y: {
      // optional selector which element to inspect
      element: '#storybook-root',
      // axe-core configurationOptions (https://github.com/dequelabs/axe-core/blob/develop/doc/API.md#parameters-1)
      config: {},
      // axe-core optionsParameter (https://github.com/dequelabs/axe-core/blob/develop/doc/API.md#options-parameter)
      options: {},
      // optional flag to prevent the automatic check
      manual: true,
    },
  },
};

export const accessible = () => <button>Accessible button</button>;

export const inaccessible = () => (
  <button style={{ backgroundColor: 'red', color: 'darkRed' }}>Inaccessible button</button>
);

Automate accessibility tests with test runner

The test runner does not apply any rules that you have set on your stories by default. You can configure the runner to correctly apply the rules by following the guide on the Storybook docs.

Roadmap

• Make UI accessible
• Show in story where violations are.
• Add more example tests
• Add tests
• Make CI integration possible