wxt/docs/guide/essentials/config/environment-variables.md

Environment Variables

Dotenv Files

WXT supports dotenv files the same way as Vite. Create any of the following files:

.env
.env.local
.env.[mode]
.env.[mode].local

And any environment variables listed inside them will be available at runtime:

# .env
VITE_API_KEY=...

await fetch(`/some-api?apiKey=${import.meta.env.VITE_API_KEY}`);

Remember to prefix any environment variables with VITE_, otherwise they won't be available at runtime, as per Vite's convention.

Built-in Environment Variables

WXT provides some custom environment variables based on the current command:

Usage	Type	Description
import.meta.env.MANIFEST_VERSION	2 │ 3	The target manifest version
import.meta.env.BROWSER	string	The target browser
import.meta.env.CHROME	boolean	Equivalent to import.meta.env.BROWSER === "chrome"
import.meta.env.FIREFOX	boolean	Equivalent to import.meta.env.BROWSER === "firefox"
import.meta.env.SAFARI	boolean	Equivalent to import.meta.env.BROWSER === "safari"
import.meta.env.EDGE	boolean	Equivalent to import.meta.env.BROWSER === "edge"
import.meta.env.OPERA	boolean	Equivalent to import.meta.env.BROWSER === "opera"

You can also access all of Vite's environment variables:

Usage	Type	Description
import.meta.env.MODE	string	The mode the extension is running in
import.meta.env.PROD	boolean	When NODE_ENV='production'
import.meta.env.DEV	boolean	Opposite of import.meta.env.PROD

:::details Other Vite Environment Variables Vite provides two other environment variables, but they aren't useful in WXT projects:

• import.meta.env.BASE_URL: Use browser.runtime.getURL instead.
• import.meta.env.SSR: Always false. :::