Live Field Validation for Gravity Forms checks each field as soon as the user finishes it and shows the result inline, without a page reload. It runs the same validation pipeline Gravity Forms uses at submission, including custom gform_field_validation filters and no-duplicates checks, so what users see live matches what happens on submit.
Choose which fields validate live from a per-form settings tab, with required and optional fields labeled. Validation state carries across multi-page forms, values populated by GP Populate Anything are handled, and a JavaScript event fires on every validated field for custom UI.