Validation

ELI5 — The Vibe Check

Validation is your backend's bouncer. Before any data gets into the database, the bouncer checks it: 'Is this email actually an email? Is this password long enough? Is this required field actually filled in?' If anything fails, the bouncer blocks it with an error.

Real Talk

Validation is the process of verifying that input data meets defined rules and constraints before processing or storing it. Backend validation is essential for data integrity and security, even when frontend validation exists, since API requests can bypass the frontend.

Show Me The Code

const schema = z.object({
  email: z.string().email(),
  age:   z.number().min(18),
  name:  z.string().min(2).max(50),
});

const result = schema.safeParse(req.body);

When You'll Hear This

"Add server-side validation for the form fields." / "Validation failed — the email format is wrong."