Form Validation

Form Validation

Bootstrap validation styles help users understand whether submitted values satisfy client-side rules, but validation must also happen on the server.

Core concept

Explain required, type constraints, needs-validation, novalidate, valid/invalid classes, invalid-feedback, and the submit event pattern. Show how browser validation and Bootstrap styling cooperate.

Using it in a real interface

Build a registration form with required name, valid email, and password rules. Explain why feedback should appear near the field and why server-side validation remains mandatory.

Implementation notes

Do not trust client-side validation for security. A malicious client can bypass JavaScript and send arbitrary HTTP requests directly to the server.