Don't assume single vs multi from visuals
dont-assume-single-vs-multi-from-visuals
Don’t assume users know single- vs multi-select from radio vs checkbox visuals alone.
Description
People should not have to infer whether they may pick one or many from radio versus checkbox visuals alone. Make single- versus multi-select explicit in copy or grouping so the choice cardinality is clear before they act. Relying only on control shape leaves room for mistaken multi-picks or missed exclusivity. Fail when only the radio or checkbox shape tells people whether one or many can be chosen. Use this wherever selection cardinality could be unclear from visuals.
When to use
Offering radio or checkbox sets where selection cardinality could be unclear.
Not when
Not for single obvious binary toggles with no multi-select risk.
Agent hint
State single- versus multi-select in copy or grouping; do not rely on shape alone.
Copy or grouping makes single- vs multi-select explicit; visuals are not the only cue.
Only the radio/checkbox shape tells people whether one or many can be chosen.
Citations
GOV.UK Design System — Radios
https://design-system.service.gov.uk/components/radios/