WCAG 2.4.13: Focus Appearance
WCAG 2.4.13 Focus Appearance is a level AAA success criterion from WCAG 2.2. The focus indicator has enough size and contrast: an area at least as large as a 2 pixel perimeter, and a 3:1 contrast change.
A one-pixel grey outline is easy to miss.
How to test
Measure the focus outline thickness and its contrast against the colours next to it.
How to fix
Use at least a 2 pixel solid outline in a dark colour.
Example that fails
The focus style is a 1 pixel #ccc outline.
Example that passes the check
The focus style is a 3 pixel #1a1714 outline.
Shopify
Set a 3 pixel solid outline on :focus-visible in the theme CSS.
WooCommerce
Replace thin focus rings in the stylesheet.
WordPress
Set a thick focus outline in the theme.
Wix
Do not weaken the default focus style with custom CSS.