Color contrast below 4.5:1 in subset of browsers and devices - WCAG pass or fail?

Hi

This came up in a discussion on an ACT-R rule.

The input fields in the code below have a passing contrast ratio in Chrome, Edge and Safari, but a failing contrast ratio of 1.18 in Firefox and IE (due to lack of support for :read-only and :read-write CSS selectors in Firefox and IE).  Support in Firefox has not been implemented due to disagreements over the spec - the Bugzilla tracking bug for these selectors is 14 years old.

It doesn’t seem to fall under the ‘Accessibility Supported’ definition since no AT is involved.

Is contrast below threshold on some (but not all) browsers a pass or fail of 1.4.3 Minimum Contrast?

<!doctype html>
<html lang="en">
<head>
    <title>Test</title>
    <style>
    body {
        color: #000;
        background-color: #fff;
    }

    /* contrast ratio 1.18 */
    input {
        color: #ddd;
        background-color: #ccc;
    }

    /*:read-only and :read-write only supported in Blink/WebKit/Edge - not supported in Firefox/IE11 */
    /* contrast ratio 16.27 */
    input:read-only {
        color: #111;
        background-color: #eee;
    }

   /* contrast ratio 21.0 */
    input:read-write {
        color: #000;
        background-color: #fff;
    }
    </style>
</head>
<body>
    <label>Read only:<input type='text' readonly value='read only text'></label>
    <label>Read write:<input type='text'  value='read write text'></label>
</body>
</html>

You can also produce exactly the same impact on end users using @supports rules, conditional comments or CSS hacks.

It’s also possible to produce have contrast failures at specific screen sizes using @media queries:

    input {
        color: #ddd;
        background-color: #ccc;
    }

    /* contrast fail on screens less than 800px wide = mobiles and tablets in portrait mode */
    @media ( min-width: 800px ) {
      input {
        color: #111;
        background-color: #eee;
      }
    }

This has exactly the same impact as the first example, except that users of specific devices are affected rather than users of specific browsers.

Is contrast below threshold on some (but not all) devices a pass or fail of 1.4.3 Minimum Contrast?

Thanks
Mark

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Mark Rogers - mark.rogers@powermapper.com<mailto:mark.rogers@powermapper.com>
PowerMapper Software Ltd - www.powermapper.com
Registered in Scotland No 362274 Quartermile 2 Edinburgh EH3 9GL

Received on Tuesday, 28 May 2019 15:32:54 UTC