Migration from v4

Node.js Support

Vite no longer supports Node.js 14 / 16 / 17 / 19, which reached its EOL. Node.js 18 / 20+ is now required.

Rollup 4

Vite is now using Rollup 4 which also brings along its breaking changes, in particular:

• Import assertions (assertions prop) has been renamed to import attributes (attributes prop).
• Acorn plugins are no longer supported.
• For Vite plugins, this.resolve skipSelf option is now true by default.
• For Vite plugins, this.parse now only supports the allowReturnOutsideFunction option for now.

Read the full breaking changes in Rollup's release notes for build-related changes in build.rollupOptions.

If you are using TypeScript, make sure to set moduleResolution: 'bundler' (or node16/nodenext) as Rollup 4 requires it. Or you can set skipLibCheck: true instead.

Deprecate CJS Node API

The CJS Node API of Vite is deprecated. When calling require('vite'), a deprecation warning is now logged. You should update your files or frameworks to import the ESM build of Vite instead.

In a basic Vite project, make sure:

1. The vite.config.js file content is using the ESM syntax.
2. The closest package.json file has "type": "module", or use the .mjs/.mts extension, e.g. vite.config.mjs or vite.config.mts.

For other projects, there are a few general approaches:

• Configure ESM as default, opt-in to CJS if needed: Add "type": "module" in the project package.json. All *.js files are now interpreted as ESM and needs to use the ESM syntax. You can rename a file with the .cjs extension to keep using CJS instead.
• Keep CJS as default, opt-in to ESM if needed: If the project package.json does not have "type": "module", all *.js files are interpreted as CJS. You can rename a file with the .mjs extension to use ESM instead.
• Dynamically import Vite: If you need to keep using CJS, you can dynamically import Vite using import('vite') instead. This requires your code to be written in an async context, but should still be manageable as Vite's API is mostly asynchronous.

See the troubleshooting guide for more information.

Rework define and import.meta.env.* replacement strategy

In Vite 4, the define and import.meta.env.* features use different replacement strategies in dev and build:

• In dev, both features are injected as global variables to globalThis and import.meta respectively.
• In build, both features are statically replaced with a regex.

This results in a dev and build inconsistency when trying to access the variables, and sometimes even caused failed builds. For example:

// vite.config.js
export default defineConfig({
  define: {
    __APP_VERSION__: JSON.stringify('1.0.0'),
  },
})

const data = { __APP_VERSION__ }
// dev: { __APP_VERSION__: "1.0.0" } ✅
// build: { "1.0.0" } ❌

const docs = 'I like import.meta.env.MODE'
// dev: "I like import.meta.env.MODE" ✅
// build: "I like "production"" ❌

Vite 5 fixes this by using esbuild to handle the replacements in builds, aligning with the dev behaviour.

This change should not affect most setups, as it's already documented that define values should follow esbuild's syntax:

To be consistent with esbuild behavior, expressions must either be a JSON object (null, boolean, number, string, array, or object) or a single identifier.

However, if you prefer to keep statically replacing values directly, you can use @rollup/plugin-replace.

General Changes

SSR externalized modules value now matches production

In Vite 4, SSR externalized modules are wrapped with .default and .__esModule handling for better interoperability, but it doesn't match the production behaviour when loaded by the runtime environment (e.g. Node.js), causing hard-to-catch inconsistencies. By default, all direct project dependencies are SSR externalized.

Vite 5 now removes the .default and .__esModule handling to match the production behaviour. In practice, this shouldn't affect properly-packaged dependencies, but if you encounter new issues loading modules, you can try these refactors:

// Before:
import { foo } from 'bar'

// After:
import _bar from 'bar'
const { foo } = _bar

// Before:
import foo from 'bar'

// After:
import * as _foo from 'bar'
const foo = _foo.default

Note that these changes matches the Node.js behaviour, so you can also run the imports in Node.js to test it out. If you prefer to stick with the previous behaviour, you can set legacy.proxySsrExternalModules to true.

worker.plugins is now a function

In Vite 4, worker.plugins accepted an array of plugins ((Plugin | Plugin[])[]). From Vite 5, it needs to be configured as a function that returns an array of plugins (() => (Plugin | Plugin[])[]). This change is required so parallel worker builds run more consistently and predictably.

Allow path containing . to fallback to index.html

In Vite 4, accessing a path in dev containing . did not fallback to index.html even if appType is set to 'spa' (default). From Vite 5, it will fallback to index.html.

Note that the browser will no longer show a 404 error message in the console if you point the image path to a non-existent file (e.g. <img src="./file-does-not-exist.png">).

Align dev and preview HTML serving behaviour

In Vite 4, the dev and preview servers serve HTML based on its directory structure and trailing slash differently. This causes inconsistencies when testing your built app. Vite 5 refactors into a single behaviour like below, given the following file structure:

├── index.html
├── file.html
└── dir
    └── index.html

Request	Before (dev)	Before (preview)	After (dev & preview)
/dir/index.html	/dir/index.html	/dir/index.html	/dir/index.html
/dir	/index.html (SPA fallback)	/dir/index.html	/index.html (SPA fallback)
/dir/	/dir/index.html	/dir/index.html	/dir/index.html
/file.html	/file.html	/file.html	/file.html
/file	/index.html (SPA fallback)	/file.html	/file.html
/file/	/index.html (SPA fallback)	/file.html	/index.html (SPA fallback)

Manifest files are now generated in .vite directory by default

In Vite 4, the manifest files (build.manifest and build.ssrManifest) were generated in the root of build.outDir by default.

From Vite 5, they will be generated in the .vite directory in the build.outDir by default. This change helps deconflict public files with the same manifest file names when they are copied to the build.outDir.

Corresponding CSS files are not listed as top level entry in manifest.json file

In Vite 4, the corresponding CSS file for a JavaScript entry point was also listed as a top-level entry in the manifest file (build.manifest). These entries were unintentionally added and only worked for simple cases.

In Vite 5, corresponding CSS files can only be found within the JavaScript entry file section. When injecting the JS file, the corresponding CSS files should be injected. When the CSS should be injected separately, it must be added as a separate entry point.

CLI shortcuts require an additional Enter press

CLI shortcuts, like r to restart the dev server, now require an additional Enter press to trigger the shortcut. For example, r + Enter to restart the dev server.

This change prevents Vite from swallowing and controlling OS-specific shortcuts, allowing better compatibility when combining the Vite dev server with other processes, and avoids the previous caveats.

Update experimentalDecorators and useDefineForClassFields TypeScript behaviour

Vite 5 uses esbuild 0.19 and removes the compatibility layer for esbuild 0.18, which changes how experimentalDecorators and useDefineForClassFields are handled.

• experimentalDecorators is not enabled by default

  You need to set compilerOptions.experimentalDecorators to true in tsconfig.json to use decorators.

• useDefineForClassFields defaults depend on the TypeScript target value

  If target is not ESNext or ES2022 or newer, or if there's no tsconfig.json file, useDefineForClassFields will default to false which can be problematic with the default esbuild.target value of esnext. It may transpile to static initialization blocks which may not be supported in your browser.

  As such, it is recommended to set target to ESNext or ES2022 or newer, or set useDefineForClassFields to true explicitly when configuring tsconfig.json.

{
  "compilerOptions": {
    // Set true if you use decorators
    "experimentalDecorators": true,
    // Set true if you see parsing errors in your browser
    "useDefineForClassFields": true,
  },
}

Remove --https flag and https: true

The --https flag sets server.https: true and preview.https: true internally. This config was meant to be used together with the automatic https certification generation feature which was dropped in Vite 3. Hence, this config is no longer useful as it will start a Vite HTTPS server without a certificate.

If you use @vitejs/plugin-basic-ssl or vite-plugin-mkcert, they will already set the https config internally, so you can remove --https, server.https: true, and preview.https: true in your setup.

Remove resolvePackageEntry and resolvePackageData APIs

The resolvePackageEntry and resolvePackageData APIs are removed as they exposed Vite's internals and blocked potential Vite 4.3 optimizations in the past. These APIs can be replaced with third-party packages, for example:

• resolvePackageEntry: import.meta.resolve or the import-meta-resolve package.
• resolvePackageData: Same as above, and crawl up the package directory to get the root package.json. Or use the community vitefu package.

import { resolve } from 'import-meta-resolve'
import { findDepPkgJsonPath } from 'vitefu'
import fs from 'node:fs'

const pkg = 'my-lib'
const basedir = process.cwd()

// `resolvePackageEntry`:
const packageEntry = resolve(pkg, basedir)

// `resolvePackageData`:
const packageJsonPath = findDepPkgJsonPath(pkg, basedir)
const packageJson = JSON.parse(fs.readFileSync(packageJsonPath, 'utf-8'))

Removed Deprecated APIs

• Default exports of CSS files (e.g import style from './foo.css'): Use the ?inline query instead
• import.meta.globEager: Use import.meta.glob('*', { eager: true }) instead
• ssr.format: 'cjs' and legacy.buildSsrCjsExternalHeuristics (#13816)
• server.middlewareMode: 'ssr' and server.middlewareMode: 'html': Use appType + server.middlewareMode: true instead (#8452)

Advanced

There are some changes which only affect plugin/tool creators.

• [#14119] refactor!: merge PreviewServerForHook into PreviewServer type
  • The configurePreviewServer hook now accepts the PreviewServer type instead of PreviewServerForHook type.
• [#14818] refactor(preview)!: use base middleware
  • Middlewares added from the returned function in configurePreviewServer now does not have access to the base when comparing the req.url value. This aligns the behaviour with the dev server. You can check the base from the configResolved hook if needed.
• [#14834] fix(types)!: expose httpServer with Http2SecureServer union
  • http.Server | http2.Http2SecureServer is now used instead of http.Server where appropriate.

Also there are other breaking changes which only affect few users.

• [#14098] fix!: avoid rewriting this (reverts #5312)
  • Top level this was rewritten to globalThis by default when building. This behavior is now removed.
• [#14231] feat!: add extension to internal virtual modules
  • Internal virtual modules' id now has an extension (.js).
• [#14583] refactor!: remove exporting internal APIs
  • Removed accidentally exported internal APIs: isDepsOptimizerEnabled and getDepOptimizationConfig
  • Removed exported internal types: DepOptimizationResult, DepOptimizationProcessing, and DepsOptimizer
  • Renamed ResolveWorkerOptions type to ResolvedWorkerOptions
• [#5657] fix: return 404 for resources requests outside the base path
  • In the past, Vite responded to requests outside the base path without Accept: text/html, as if they were requested with the base path. Vite no longer does that and responds with 404 instead.
• [#14723] fix(resolve)!: remove special .mjs handling
  • In the past, when a library "exports" field maps to an .mjs file, Vite will still try to match the "browser" and "module" fields to fix compatibility with certain libraries. This behavior is now removed to align with the exports resolution algorithm.
• [#14733] feat(resolve)!: remove resolve.browserField
  • resolve.browserField has been deprecated since Vite 3 in favour of an updated default of ['browser', 'module', 'jsnext:main', 'jsnext'] for resolve.mainFields.
• [#14855] feat!: add isPreview to ConfigEnv and resolveConfig
  • Renamed ssrBuild to isSsrBuild in the ConfigEnv object.
• [#14945] fix(css): correctly set manifest source name and emit CSS file
  • CSS file names are now generated based on the chunk name.

Migration from v3

Check the Migration from v3 Guide in the Vite v4 docs first to see the needed changes to port your app to Vite v4, and then proceed with the changes on this page.