Perceivable Techniques

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Small Screen Size

  • Ensuring that navigation works on different screen sizes (M014)
  • Providing vertical navigation mechanisms that work without horizontal scrolling on narrow width screens (M016)
  • Providing the open/closed state information in the menu icon (M017)
  • Ensure best presentations of captions (either default visible or visible control on mobile) - from Detlev
  • size of captions on mobile devices


  • Ensuring that menu can be zoomed to 200% (M018)
    • Menus in particular may present unique challenges when content is magnified to 200%. This may occur because menus often appear vertically and accessing menu items that scroll out of the viewable area may be truncated and/or may present challenges such as menus may disappear when the user scrolls the viewable area.
    • We don't want to imply that 200% is somehow a number that makes it accessible. It's more of a threshold that we have to realistically say once you get to too big you have a very small number of characters or words that appear on the screen so for that reason we don't test above that
  • Setting viewport meta setting to allow magnification to 200% (M021)
  • Supporting the characteristic properties of the platform (e.g. zoom, larger font, captions) (M007)
    • More applicable to native apps
    • Need to do some more research around media players (caption font sizes)
    • Using Apple system font provides the larger font size in Safari
  • Providing a way for users to change font size (M013)
  • Ensure snap scrolling does not prevent access to content with resize of text
  • Ensure fixed position content does not prevent access to content when text is resized.
    • e.g. from a device such as an iPhone.


Situation A - text is less than 1.5 times default text size or is less than 1.2 times the default text size and bold

  • Ensuring that a contrast ratio of at least 4.5:1 exists between text (and images of text) and background behind the text

Situation B - text is 1.5 times default text size or is 1.2 times the default text size and bold

  • Ensuring that a contrast ratio of at least 3:1 exists between text (and images of text) and background behind the text

Non Linear Screen Layout

  • Managing accessibility for non-linear screen layouts (from Jan) -- to give guidance for very complex mobile pages, including pages that may ignore the DOM, where there is content being swiped in from the sides.
    • Anything working outside the DOM must communicate it to the accessibilityAPI
    • Correct affordances so that people know where there is an operation available from the side swipe
    • Meaningful sequence and focus order with a side swipe - i.e. when menus are swiped in
    • Point of regard - don't lose your current location on main page with a side swipe in/out (i.e. menu swiping in)
    • Considerations for items that steal focus (an advertisement for example). 3.2.1 On Focus 3.2.2 On Input 2.2.2 Pause, stop, hide - auto updating. "If you take an action and a message pops up about that action the message will pop up and become part of the swipe order on that screen – it's something the user initiated but it's not necessarily happening instantly it's happening sometime later - another example is pop up banner ads that you don't want to take focus to, but that's just the way the website works"


  • M19: Providing media metadata
    • Future consideration
    • Check if there is anything in UAAG (Jeanne)