Lesson 4.217mIntermediate8.8k students

Forms, validation, and error states

Client-side validation is a convenience; the server check is the real one. Parse the payload on arrival and return errors the form can render.

This lesson sits in Server Actions and Mutations, part of Next.js App Router in Depth. It assumes what came before it and leads directly into the next lesson in the module.

In this lesson you will

  • Validate submitted data on the server before writing
  • Return structured field errors back to the form
  • Keep the form usable when JavaScript has not loaded

Pro tip

Never trust the shape of an incoming payload. Parse it, then use the parsed value.

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