For your safety, Snowpack supports only environment variables which begin with SNOWPACK_PUBLIC_*. We do this because everything in your web application is sent to the browser, and we don't want you to accidentally share sensitive keys/env variables with your public web application. Prefixing your frontend web env variables with SNOWPACK_PUBLIC_ is a good reminder that they will be shared with the world.

Setting environment variables

You can set environment variables with snowpack in three different ways:

Option 1: CLI

Set environment variables when you run the snowpack CLI:

SNOWPACK_PUBLIC_API_URL=api.google.com snowpack dev

Option 2: Config file

New in v3.1.0 Pass environment variables as an object to the env property. Note that these environment variables do not need to use the SNOWPACK_PUBLIC_ prefix and anything set here will be available on __SNOWPACK_ENV__ (see below).

// snowpack.config.mjs
export default {
  env: {
    API_URL: 'api.google.com',
  },
};

In prior versions, we recommended setting environment variables by adding to process.env.* at the top of your snowpack.config.mjs file. This ended up being pretty confusing, so using the env property is now the recommended approach.

// snowpack.config.mjs
process.env.SNOWPACK_PUBLIC_API_URL = 'api.google.com';
// ...rest of config

Option 3: Plugin

Use a plugin such as plugin-dotenv to load environment variables from a .env file.

Reading environment variables

You can read environment variables directly in your web application via __SNOWPACK_ENV__. If you've ever used process.env in Create React App or any Webpack application, this behaves exactly the same.

// `__SNOWPACK_ENV__` - Read process.env variables in your web app
fetch(`${__SNOWPACK_ENV__.SNOWPACK_PUBLIC_API_URL}/users`).then(...)

// Supports destructuring as well:
const {SNOWPACK_PUBLIC_API_URL} = __SNOWPACK_ENV__;
fetch(`${SNOWPACK_PUBLIC_API_URL}/users`).then(...)

// Instead of `__SNOWPACK_ENV__.NODE_ENV` use `__SNOWPACK_ENV__.MODE`
if (__SNOWPACK_ENV__.MODE === 'development') {
  // ...

__SNOWPACK_ENV__.MODE and __SNOWPACK_ENV__.NODE_ENV are also both set to the current process.env.NODE_ENV value, so that you can change app behavior based on dev vs. build. The env value is set to development during snowpack dev, and production during snowpack build. Use this in your application instead of process.env.NODE_ENV.

You can also use environment variables in HTML files. All occurrences of %SNOWPACK_PUBLIC_*%, %PUBLIC_URL%, and %MODE% will be replaced at build time.

Remember: that these env variables are statically injected into your application for everyone at build time, and not runtime.