Skip to main content
UI Guides

Search rules

Search all UI Guides rules by name, category, or source

formsRauno

Lean on Native Constraint Validation

SHOULD

SHOULD: Lean on native constraint validation (`required`, `type="email"`, `pattern`, `min`, `minlength`) instead of hand-rolled JS checks; drop `noValidate` and reach for `setCustomValidity` only for rules HTML cannot express.

Use required, type, pattern, min and max so the browser validates instead of hand-rolling every check in JS

Bad

Good

Why it matters

The platform already ships constraint validation: required, type="email", pattern, min, max and minlength are enforced by the browser on every submit path — click, Enter, autofill, programmatic — and it focuses the first offending control and announces the message to assistive tech for free. Hand-rolled JS checks miss those paths (a keyup handler never fires on a mouse paste), and hand-rolled email regexes routinely reject valid addresses like ada+work@example.com.

Keep the submit button enabled and drop noValidate; reach for the Constraint Validation API (setCustomValidity, ValidityState) only for the rules HTML cannot express.

References

Built by Gleb Stroganov, design engineer at Evil Martians.

The rules come from other people's skills and guidelines — Vercel, Rauno Freiberg, @Ibelick, impeccable, Emil Kowalski, Tailwind, RAMS — each one credited on the Sources page. The work here is extraction and wiring: every rule is pulled into one corpus, given a good and a bad example you can operate, a MUST/SHOULD/NEVER rule an agent can paste, and a link back to where it came from.