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Almost, but not quite a guide to accessibility requirements
1 Perceivable

1.3.2 Meaningful Sequence

Conformance level: A
Criterion released in WCAG version: 2.0

Official description of the success criterion

When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined.

What to do?

Ensure that content is presented in a meaningful order.

It's optimal if the DOM order matches the visual order.

Why is it important?

Assists users who rely on assistive technologies to understand the content.

Common pitfalls

There are some common failures for this:

  • Using white space characters to create table-like or column-like content.
  • Changing the meaning of content by positioning information with CSS.
  • Poor HTML structure, for example using layout tables that don't provide the same information when they are read linearly.
How to test for it?

Check the reading order and ensure it makes sense. One way to do this is to remove the CSS styles from the page and check if the content is understandable without the visual styles.

How to take this criterion into account in development?
  • Use semantic HTML, don't modify the visual layout of the content only with CSS. For example, if you need a list element, use a list element instead of styling a set of spans or divs to look like a list.
  • Adopt a left-justified approach for languages that read from left to right (e.g. English), and right-justified for languages that read right to left (e.g. Arabic).
  • Make the DOM order always match the visual order when possible.
  • Often, navigational elements may change place in relation to the content in comparison to the view created by CSS. This does not necessarily make the reading order illogical.
  • Place paragraphs of content in a meaningful and correct order.
  • Use section headings or sub-headings to highlight importance.
  • Don't use whitespace characters to position content.
  • Allocate the appropriate listing type (such as order and nesting) to content.

More about this criterion elsewhere