On Focus
When any UI component receives focus, it must not initiate a change of context — no surprise navigation, no popup opening, no form submission triggered by focus alone.
What it requires
WCAG 2.0 SC 3.2.1 prevents disorienting "focus surprises". Common failure: a country-selector dropdown that auto-submits on focus rather than waiting for explicit selection. Keyboard users tabbing through the form get yanked to a new page just by passing through the field.
Context changes (popups, navigation, form submission) must be triggered by an explicit user action — click, Enter key, or button activation — not by focus alone.
Common Shopify failure
Country/region selector that uses `onfocus="this.form.submit()"` to immediately reload the page when a keyboard user tabs into it. Custom autocomplete that opens a popup on focus rather than on input.
How to fix it
AccessComply rewrites `onfocus` handlers that change context, and converts focus-only autocomplete triggers to input-triggered ones.
Primary source: W3C — WCAG 2.0 Understanding 3.2.1