Form Validation

Form validation checks whether information entered into a form meets requirements needed to process it. A quote request form might check whether a required email field is filled in or whether a phone number has an acceptable format. Validation can run in the browser, on the server, or both; server-side checks remain important even when the browser shows immediate feedback. Good validation explains which field needs attention and how to fix it without erasing information already entered. It should not reject legitimate names, addresses, or phone formats because of overly narrow assumptions. Validation improves data quality, while a clear error message helps the visitor recover when a check fails.