wagtail/client/scss/overrides/_utilities.focus.scss

// stylelint-disable declaration-no-important
// Set global focus outline styles so they are consistent across the UI,
// without individual components having to explicitly define focus styles.
// Using !important because we want to enforce only one style is used across the UI.
*:focus-visible {
  outline: $focus-outline-width solid theme('colors.focus') !important;
}