Custom Validation

Prisma Client has type-safety and run-time type validation but does not include validation for user input.

This means you can use any validation library you'd like. The Node.js ecosystem offers a number of high-quality, easy-to-use validation libraries to choose from including: joi, validator.js, Yup, Zod and Superstruct.

Custom Signup Validation

Here's an example using Superstruct to validate that the data needed to signup a new user is correct:

import { PrismaClient, Prisma, User } from '@prisma/client'
import { assert, object, string, size, refine } from 'superstruct'
import isEmail from 'isemail'
const prisma = new PrismaClient()
// Runtime validation
const Signup = object({
// string and a valid email address
email: refine(string(), 'email', (v) => isEmail.validate(v)),
// password is between 7 and 30 characters long
password: size(string(), 7, 30),
// first name is between 2 and 50 characters long
firstName: size(string(), 2, 50),
// last name is between 2 and 50 characters long
lastName: size(string(), 2, 50),
type Signup = Omit<Prisma.UserCreateArgs['data'], 'id'>
// Signup function
async function signup(input: Signup): Promise<User> {
// Assert that input conforms to Signup, throwing with a helpful
// error message if input is invalid.
assert(input, Signup)
return prisma.user.create({
data: input.user,

The example above shows how you can create a custom type-safe signup function that ensures the input is valid before creating a user.

Going Further

  • Learn how you how can organize your code better by moving the signup function into a custom model.
  • There's an outstanding feature request to bake user validation into Prisma Client. If you'd like to see that happen, make sure to upvote that issue and share your use case!
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