Inline validation
Form-field feedback that appears as the user types, rather than waiting until they submit.
When a field is invalid (or valid), inline validation surfaces the state immediately — usually next to the field with a colored icon, message, or border. Done well, it catches errors early; done poorly, it nags users while they're mid-typing. The standard practice is to validate on blur for errors and on input for success/length cues.
Also called
live validationreal-time validation
When to use
- Fields with strict format requirements (email, phone, password complexity)
- Long forms where catching errors at submit time wastes user time
- Sign-up flows where typo recovery matters
When not to use
- Short, low-stakes forms where on-submit validation is fine
- Fields where checking on every keystroke would feel intrusive (validate on blur instead)
Related
Source
Form design vernacular; Luke Wroblewski's research on form usability popularized the pattern in the late 2000s.