On Focus
When any user interface component receives focus, it does not initiate a change of context.
In plain language
Simply moving keyboard focus to an element (like tabbing onto it) should never, by itself, trigger a big change — like opening a new window, submitting a form, or jumping to a different page.
Why it matters
Keyboard users move focus around constantly just to explore a page. If merely landing on an element unexpectedly changes context, they lose their place, get confused, or trigger actions they didn't intend.
In practice
Fails this criterion
Tabbing onto a form field automatically opens a help pop-up and moves focus into it, interrupting the user's navigation without them asking for it.
Meets this criterion
The same field can show helpful information without moving focus or opening anything — the pop-up only appears if the user explicitly asks for it, like pressing a help button.
Test it yourself
Tab through the page's interactive elements one by one, without pressing Enter or activating anything. If just landing on an element changes the page, opens something, or moves you elsewhere, this criterion is failing.