Mobile accessibility checklist - Accessibility 编辑

This document provides a concise checklist of accessibility requirements for mobile app developers. It is intended to continuously evolve as more patterns arise.

Color

• Color contrast must comply with WCAG 2.1 AA level requirements:
  • Contrast ratio of 4.5:1 for normal text (less than 18 point or 14 point bold.)
  • Contrast ratio of 3:1 for large text (at least 18 point or 14 point bold.)
• Information conveyed via color must be also available by other means too (underlined text for links, etc.)

Visibility

• Content hiding techniques such as zero opacity, z-index order and off-screen placement must not be used exclusively to handle visibility.
• Everything other than the currently visible screen must be truly invisible (especially relevant for single page apps with multiple cards):
  • Use the hidden attribute or visibility or display style properties.
  • Unless absolutely unavoidable, aria-hidden attribute should not be used.

Focus

• All activatable elements must be focusable:
  • Standard controls such as links, buttons, and form fields are focusable by default.
  • Non-standard controls must have an appropriate ARIA Role assigned to them, such as button, link, or checkbox.
• Focus should be handled in a logical order and consistent manner.

Text equivalents

• Text equivalent must be provided for every non-strictly presentational non-text element within the app.
  • Use alt and title where appropriate (see Steve Faulkner's post about Using the HTML title attribute for a good guide.)
  • If the above attributes are not applicable, use appropriate ARIA States and Properties such as aria-label, aria-labelledby, or aria-describedby.
• Images of text must be avoided.
• All user interface components with visible text (or image of text) as labels must have the same text available in the programmatic name of the component. WCAG 2.1: Label in name.
• All form controls must have labels (<label> elements) for the benefit of screen reader users.

Handling state

• Standard controls such as radio buttons and checkboxes are handled by the operating system. However, for other custom controls state changes must be provided via ARIA States such asaria-checked, aria-disabled, aria-selected, aria-expanded, and aria-pressed.

Orientation

• Content should not be restricted to a single orientation, such as portrait or landscape, unless essential. WCAG 2.1: Orientation
  • Examples of when an orientation is esssential is a piano application or a bank check.

General guidelines

• An app title must be provided.
• Headings must not break hierarchical structure

  <h1>Top level heading</h1>
    <h2>Secondary heading</h2>
    <h2>Another secondary heading</h2>
      <h3>Low level heading</h3>

• ARIA Landmark Roles should be used to describe an app or document structure, such as banner, complementary, contentinfo, main, navigation, search.
• For touch events, at least one of the following must be true (WCAG 2.1: Pointer Cancellation):
  • The down-event should not be used to trigger any action
  • The action is triggered on the up event and an option to abort the action before its completion is available or an option to undo the action after its completion
  • The up-event will undo any action that was triggered on a down event
  • It is essential to trigger the action on the down event. For example, playing a game or a piano application.
• Touch targets must be large enough for the user to interact with (see the BBC Mobile Accessibility Guidelines for useful touch target size guidelines).

Note: The original version of this document was written by Yura Zenevich.