Next.js

The Next.js package comes preconfigured for Next.js and also enforces some extra rules by default to make sure you have out-of-the-box compatibility in all different Next.js runtimes.

Install dependencies

Install the required dependencies:

pnpm add @t3-oss/env-nextjs zod

pnpm add @t3-oss/env-nextjs zod

Create your schema

src/env.mjs

import { createEnv } from "@t3-oss/env-nextjs";
import { z } from "zod";
 
export const env = createEnv({
  server: {
    DATABASE_URL: z.string().url(),
    OPEN_AI_API_KEY: z.string().min(1),
  },
  client: {
    NEXT_PUBLIC_PUBLISHABLE_KEY: z.string().min(1),
  },
  runtimeEnv: {
    DATABASE_URL: process.env.DATABASE_URL,
    OPEN_AI_API_KEY: process.env.OPEN_AI_API_KEY,
    NEXT_PUBLIC_PUBLISHABLE_KEY: process.env.NEXT_PUBLIC_PUBLISHABLE_KEY,
  },
});

src/env.mjs

import { createEnv } from "@t3-oss/env-nextjs";
import { z } from "zod";
 
export const env = createEnv({
  server: {
    DATABASE_URL: z.string().url(),
    OPEN_AI_API_KEY: z.string().min(1),
  },
  client: {
    NEXT_PUBLIC_PUBLISHABLE_KEY: z.string().min(1),
  },
  runtimeEnv: {
    DATABASE_URL: process.env.DATABASE_URL,
    OPEN_AI_API_KEY: process.env.OPEN_AI_API_KEY,
    NEXT_PUBLIC_PUBLISHABLE_KEY: process.env.NEXT_PUBLIC_PUBLISHABLE_KEY,
  },
});

Unlike in the core package, runtimeEnv is strict by default, meaning you'll have to destructure all the keys manually. This is due to how Next.js bundles environment variables and only explicitely accessed variables are included in the bundle. Missing keys will result in a type-error:

missing runtimeEnv

Validate schema on build (recommended)

We recommend you importing your newly created file in your next.config.mjs. This will make sure your environment variables are validated at build time which will save you a lot of time and headaches down the road.

next.config.mjs

import "./src/env.mjs";
 
/** @type {import("next").NextConfig} */
const config = {
  /** ... */
};
 
export default config;

next.config.mjs

import "./src/env.mjs";
 
/** @type {import("next").NextConfig} */
const config = {
  /** ... */
};
 
export default config;

Use your schema

Then, import the env object in your application and use it, taking advantage of type-safety and auto-completion:

some-api-endpoint.ts

import { env } from "~/env"; // On server
 
export const GET = async () => {
  // do fancy ai stuff
  const magic = await fetch("...", {
    headers: { Authorization: env.OPEN_AI_API_KEY },
  });
  // ...
};

some-api-endpoint.ts

import { env } from "~/env"; // On server
 
export const GET = async () => {
  // do fancy ai stuff
  const magic = await fetch("...", {
    headers: { Authorization: env.OPEN_AI_API_KEY },
  });
  // ...
};

some-component.tsx

import { env } from "~/env"; // On client - same import!
 
export const SomeComponent = () => {
  return (
    <SomeProvider publishableKey={env.PUBLIC_PUBLISHABLE_KEY}>
      {/* ... */}
    </SomeProvider>
  );
};

some-component.tsx

import { env } from "~/env"; // On client - same import!
 
export const SomeComponent = () => {
  return (
    <SomeProvider publishableKey={env.PUBLIC_PUBLISHABLE_KEY}>
      {/* ... */}
    </SomeProvider>
  );
};