What the standard says
If a web page can be navigated sequentially and the navigation sequences affect meaning or operation, focusable components receive focus in an order that preserves meaning and operability.
Why it matters
If focus jumps from the header to the footer and back, the page stops being navigable even though every control is reachable.
What a failure looks like
- failsPositive `tabindex` values (`tabindex="3"`) that reorder the whole page.
- failsA modal that opens without moving focus into it.
- failsFocus not returning to the trigger after a dialog closes.
How to fix it
- doNever use a positive `tabindex`. Fix the DOM order instead.
- doOn opening a dialog, move focus to it; on closing, return focus to what opened it.
How A11ySignal checks it
manual
No automated rule can judge this criterion, and we will not pretend otherwise. A clean scan does not mean 2.4.3 passes — it means nothing we can measure fails. This one needs a person.
What a tool cannot tell you
Tab through the page and watch where the ring goes. That is the whole test.