# Environment Variables With $env — Svelte / SvelteKit

Source: https://www.skillbyai.com/en/svelte/d-env

> Static, dynamic, public and private.

## Four $env modules

SvelteKit exposes environment variables through four modules. `$env/static/private` and `$env/static/public` are **inlined at build time**, which enables dead-code elimination; `$env/dynamic/private` and `$env/dynamic/public` are read at **run time**, which suits values that differ between deployments of the same build. Only variables starting with the public prefix (`PUBLIC_` by default) can be imported from the public modules and reach the browser. Private modules can only be imported in server-only code; importing them into client code is a build error. Locally, values come from `.env` files loaded by Vite; in production, from the platform.

## Using the right module

Server secret and public base URL.

```typescript
// .env (not committed)
// DATABASE_URL=postgres://...
// STRIPE_SECRET_KEY=sk_test_...
// PUBLIC_API_BASE=https://api.example.com

// src/lib/server/db.ts  (server-only)
import { DATABASE_URL } from '$env/static/private';
import { createClient } from './driver'; // your database client library
export const db = createClient(DATABASE_URL);

// src/routes/+page.server.ts
import { env } from '$env/dynamic/private';
const featureFlag = env.FEATURE_NEW_CHECKOUT === 'true';

// src/lib/api.ts  (can run in the browser)
import { PUBLIC_API_BASE } from '$env/static/public';
export const api = (path: string) => fetch(`${PUBLIC_API_BASE}${path}`);
```

## A safe and a notice board

Private variables stay in the server-room safe; only notes marked PUBLIC_ are pinned on the notice board that every visitor can read.

**Quiz:** Which variable can be imported into code that runs in the browser?

- [ ] DATABASE_URL from $env/static/private
- [x] PUBLIC_API_BASE from $env/static/public
- [ ] Any variable from $env/dynamic/private
- [ ] process.env.SECRET_KEY

*Answer:* PUBLIC_API_BASE from $env/static/public. Only public-prefixed variables reach the client.