Configuring Vite #

When running vite from the command line, Vite will automatically try to resolve a config file named vite.config.js inside project root.

The most basic config file looks like this:

// vite.config.js
export default {
  // config options
}

Note Vite supports using ES modules syntax in the config file even if the project is not using native Node ESM via type: "module". In this case, the config file is auto pre-processed before load.

You can also explicitly specify a config file to use with the --config CLI option (resolved relative to cwd):

vite --config my-config.js

const __filename = 'value' // SyntaxError: Identifier '__filename' has already been declared

const func = () => {
  const __filename = 'value' // no error
}

Config Intellisense #

Since Vite ships with TypeScript typings, you can leverage your IDE's intellisense with jsdoc type hints:

/** @type {import('vite').UserConfig} */
export default {
  // ...
}

Alternatively, you can use the defineConfig helper which should provide intellisense without the need for jsdoc annotations:

import { defineConfig } from 'vite'

export default defineConfig({
  // ...
})

Vite also directly supports TS config files. You can use vite.config.ts with the defineConfig helper as well.

Conditional Config #

If the config needs to conditionally determine options based on the command (dev/serve or build), the mode being used, or if it is an SSR build (ssrBuild), it can export a function instead:

export default defineConfig(({ command, mode, ssrBuild }) => {
  if (command === 'serve') {
    return {
      // dev specific config
    }
  } else {
    // command === 'build'
    return {
      // build specific config
    }
  }
})

It is important to note that in Vite's API the command value is serve during dev (in the cli vite, vite dev, and vite serve are aliases), and build when building for production (vite build).

Only ssrBuild is included instead of a more general ssr flag because, during dev, the config is shared by the single server handling SSR and non-SSR requests.

Async Config #

If the config needs to call async function, it can export a async function instead:

export default defineConfig(async ({ command, mode }) => {
  const data = await asyncFunction()
  return {
    // vite config
  }
})

Environment Variables #

Environmental Variables can be obtained from process.env as usual.

Note that Vite doesn't load .env files by default as the files to load can only be determined after evaluating the Vite config, for example, the root and envDir options affects the loading behaviour. However, you can use the exported loadEnv helper to load the specific .env file if needed.

import { defineConfig, loadEnv } from 'vite'

export default defineConfig(({ command, mode }) => {
  // Load env file based on `mode` in the current working directory.
  // Set the third parameter to '' to load all env regardless of the `VITE_` prefix.
  const env = loadEnv(mode, process.cwd(), '')
  return {
    // vite config
    define: {
      __APP_ENV__: env.APP_ENV
    }
  }
})