Who this affects
Positive tabindex values are used, which override the natural tab order and usually produce a confusing focus sequence.
How to fix it
Use tabindex="0" or no tabindex at all, and control order with DOM order.
Effort Medium · ~30-60 min
Before and after
Fails
<div class="card" tabindex="3">…</div>Passes
<div class="card" tabindex="0">…</div>How to check it by hand
Put the mouse down. Tab from the top of the page to the bottom. Every interactive element must be reachable, must show a visible focus indicator, and you must be able to tab back out of anything you tab into.
Automated testing settles roughly a third of the WCAG success criteria. This rule is one an automated tool detects reliably — but a clean automated result is not proof of conformance.
Reference
Deque's technical write-up for this rule: tabindex
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