Offer a working switch to high-contrast view
G174 offers a link or control leading to a version of the content that meets a higher contrast ratio. W3C attaches three conditions and all three matter. The control itself has to meet the contrast requirement you are claiming. The new page has to carry the same information and functionality. And it has to conform at that level on every criterion, not only the contrast ones. This is a sufficient technique for 1.4.3 Contrast (Minimum) at Level AA, and W3C also lists it at 1.4.11 Non-text Contrast, another Level AA rule, when it is used to identify interface components. Placement is advice rather than a condition. W3C says a prominent link helps people, which is true and is not part of the test.
How we find it in an audit
Our reviewers use the switch, then audit the destination as a page in its own right. Does it carry everything the original does? Does it pass at the level being claimed? We check the control too, because a pale grey link to the high-contrast view is a joke at the expense of the people who need it. Persistence across pages gets tested, since a per-page toggle is unusable on a site of any size.
How affected users experience it
Low-contrast text is a daily tax for readers with low vision, older readers, and anyone on a poor screen or in bright light. A high-contrast alternate helps, and it only helps if they can find the control before they have given up on the page. It also has to lead somewhere complete. Landing on a readable version that has lost the booking form is a different kind of failure.
Passes vs. fails
Passes
A clearly visible 'High contrast' toggle in the header, announced to assistive technology, restyles the whole site to 7:1 text and persists across pages.
Fails
Light-grey text at 2.8:1 everywhere, and the 'accessibility view' link is itself pale grey in the footer.
How this gets tested
The W3C publishes test rules that define what a checker looks for here.
- Text has enhanced contrastA tool can check this
- Text has minimum contrastA tool can check this
Other ways to satisfy this rule
7 guides on this site are filed under 1.4.3 Contrast (Minimum). W3C lists this one as sufficient for that rule on its own. Implement it correctly, in a way your readers' software actually supports, and the rule is met.
- G18sufficientMeet the 4.5:1 contrast ratio for text
- G145sufficientGive large text at least 3:1 contrast
- G148sufficientLeave text colors default, or set both
- G156advisoryKeep text recolorable by the user's browser
- F24failureNever set text color without its background
- F83failureDo not set text over a low-contrast background image
This guide is our interpretation of W3C technique G174: Providing a control with a sufficient contrast ratio that allows users to switch to a presentation that uses sufficient contrast. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.