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 (other JS and TS extensions are also supported).

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, e.g. type: "module" in package.json. 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

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 supports TypeScript config files. You can use vite.config.ts with the defineConfig helper function above, or with the satisfies operator:

import type { UserConfig } from 'vite'

export default {
  // ...
} satisfies UserConfig

Conditional Config

If the config needs to conditionally determine options based on the command (serve or build), the mode being used, if it's an SSR build (isSsrBuild), or is previewing the build (isPreview), it can export a function instead:

export default defineConfig(({ command, mode, isSsrBuild, isPreview }) => {
  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).

isSsrBuild and isPreview are additional optional flags to differentiate the kind of build and serve commands respectively. Some tools that load the Vite config may not support these flags and will pass undefined instead. Hence, it's recommended to use explicit comparison against true and false.

Async Config

If the config needs to call async functions, it can export an async function instead. And this async function can also be passed through defineConfig for improved intellisense support:

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

Using Environment Variables in Config

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 affect 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__: JSON.stringify(env.APP_ENV),
    },
  }
})