Mobile accessibility checklist

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 2.2 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 (read 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 as aria-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 essential is a piano application or a bank check.

General guidelines

• An app title must be provided.

• Headings must not break hierarchical structure

  html

  <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, ensure the following (WCAG 2.1: Pointer Cancellation):

  • The down-event should not be used to execute any part of the function;
  • Failing the above, completion of the function should be on the up-event, and a mechanism is available to abort the action before its completion or to undo the action after its completion;
  • Failing the above, the up-event should be able to undo any action that was triggered on a down event;
  • All the above may be violated if it is essential to trigger the action on the down event, usually to simulate real-world experiences or to provide real-time feedback. For example, game controls, piano keyboards, or virtual keyboards.

• Touch targets must be large enough for the user to interact with (see the BBC Mobile Accessibility Guidelines for useful touch target size guidelines).