This document provides a concise checklist of accessibility requirements for mobile app developers. It is intended to continuously evolve as more patterns arise.
- Colour 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 colour MUST be also available by other means too (underlined text for links, etc.)
- 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
- Unless absolutely unavoidable,
aria-hiddenattribute SHOULD NOT be used.
- USE the
- 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
- Focus should be handled in a logical order and consistent manner.
- Text equivalent MUST be provided for every non-strictly presentational non-text element within the app.
- 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.
- 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
- 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 cheque.
- 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
- 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).