In a multi-step form, validation should occur at each step to ensure data integrity and user experience.
Firstly, implement client-side validation using JavaScript or similar technologies. This provides immediate feedback to the user and reduces server load by preventing invalid submissions. However, it’s not foolproof as users can disable JavaScript.
Secondly, use server-side validation. Regardless of client-side checks, always validate on the server because malicious users could bypass front-end validations. Use language-specific methods for this, like PHP’s filter_var() function or Django’s form.is_valid() method in Python.
