Switch

From the Base UI reference for Switch and the installed SwitchRoot and useButton. "From" says who does it.

Switch adds no keys of its own.

What axe won't catch, from the contract, each with how this component meets it:

• Everything the eye is told, the ear is told, for every shape each prop accepts: the thumb's place and the track's fill are aria-checked, heard as on or off after the name; a disabled switch's tertiary colours are aria-disabled, heard as dimmed; a read-only switch is aria-readonly; an invalid one's danger edge is aria-invalid, with the Field's message as its description.
• Every landmark and named region has an accessible name: none here; a switch is neither. Its own name comes from the caller, which every story gives (CR-3).
• Every default label can be overridden: none here; the switch owns no strings.
• Every shape the type accepts renders, in every variant: the switch takes no ReactNode prop; every combination of checked, disabled and readOnly renders, as the stories show.
• A hidden copy kept for animation is aria-hidden, and a collapsed region is inert: the hidden input is Base UI's, aria-hidden and out of the tab order; nothing collapses.
• Native semantics first: Base UI's role="switch" on a <span>, with a native <input type="checkbox"> beside it for the label and the form; with render and nativeButton, a native <button>.
• Focus moves in reading order and returns on close: the switch is one tab stop in document order, focus stays on it when it toggles, and a click on its label moves focus to it; it opens nothing to return from.
• Every target is at least size.target-min square: the smallest target is the track itself, 40 × 24 px, and a wrapping <label> makes its text a target too.
• Loops stop when the system asks for less motion: no loop; the thumb's slide and the fill's change are transitions over duration.switch, which the tokens shorten to 0.01 ms under reduced motion (CR-6).

The switch shows no "On" or "Off" word, though Accessibility asks toggles to say their state in words as well as in looks. That rule asks for the state once, either in words that change on a plain button, such as "Follow" and "Following", or from the role of a control whose label stays the same; a switch's label names the setting and stays the same, Base UI's role="switch" says on or off to the ear in every locale with no word of Perron's, and the eye gets the thumb's place as well as the fill, so the state never rests on colour alone. A word beside every switch would also lengthen each settings row in Danish, and the caller can still write one in the label.

No owned strings: every word comes from the caller, as the label or aria-label.

For a caller using the component, with the reason. Each row is a rule: a must row's Don't is never right, a should row's needs a reason, and Checked by says what catches the Don't in a caller's code.