Could not auto-determine entry point from rollupOptions

JavaScript

Rollup

Entry Point

Module Bundler

Error Resolution

Could not auto-determine entry point from rollupOptions

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Introduction

The error Could not auto-determine entry point from rollupOptions occurs in Vite (which uses Rollup internally) when the build configuration does not specify an entry point and Vite cannot find a default index.html file in the project root. This typically happens when building a library without configuring build.lib, when the root directory is misconfigured, or when using Vite for a non-standard project structure. The fix is to explicitly set the entry point in build.rollupOptions.input or configure build.lib for library mode.

The Error

1[vite]: Rollup failed to resolve import
2Error: Could not auto-determine entry point from rollupOptions.
3You must either specify input in rollupOptions, or use the "root" option
4to point to a directory with an index.html file.

How Vite Determines the Entry Point

Vite's default behavior for finding the entry point:

Look for index.html in the project root (or the directory specified by root)
Parse index.html for <script type="module" src="..."> tags
Use those script sources as Rollup entry points

If no index.html exists or it does not contain a module script, Vite cannot determine the entry point.

Fix 1: Add `index.html` (Standard Vite App)

html

1<!-- index.html in project root -->
2<!DOCTYPE html>
3<html lang="en">
4<head>
5    <meta charset="UTF-8">
6    <meta name="viewport" content="width=device-width, initial-scale=1.0">
7    <title>My App</title>
8</head>
9<body>
10    <div id="app"></div>
11    <script type="module" src="/src/main.js"></script>
12</body>
13</html>

The <script type="module" src="/src/main.js"> tag tells Vite to use src/main.js as the entry point.

Fix 2: Specify `rollupOptions.input` (Custom Entry)

javascript

1// vite.config.js
2import { defineConfig } from 'vite'
3import { resolve } from 'path'
4
5export default defineConfig({
6  build: {
7    rollupOptions: {
8      input: resolve(__dirname, 'src/main.js')
9    }
10  }
11})

Multiple Entry Points (Multi-Page App)

javascript

1// vite.config.js
2import { defineConfig } from 'vite'
3import { resolve } from 'path'
4
5export default defineConfig({
6  build: {
7    rollupOptions: {
8      input: {
9        main: resolve(__dirname, 'index.html'),
10        admin: resolve(__dirname, 'admin.html'),
11        login: resolve(__dirname, 'login/index.html')
12      }
13    }
14  }
15})

Fix 3: Configure `build.lib` (Library Mode)

When building a library (not an application), use library mode instead of relying on index.html:

javascript

1// vite.config.js
2import { defineConfig } from 'vite'
3import { resolve } from 'path'
4
5export default defineConfig({
6  build: {
7    lib: {
8      entry: resolve(__dirname, 'src/index.js'),
9      name: 'MyLibrary',
10      fileName: (format) => `my-library.${format}.js`,
11      formats: ['es', 'umd']
12    },
13    rollupOptions: {
14      // Externalize dependencies that shouldn't be bundled
15      external: ['react', 'react-dom'],
16      output: {
17        globals: {
18          react: 'React',
19          'react-dom': 'ReactDOM'
20        }
21      }
22    }
23  }
24})

Fix 4: Set the `root` Option

If your index.html is not in the project root:

1project/
2├── app/
3│   ├── index.html        ← Entry HTML is here
4│   └── src/
5│       └── main.js
6├── vite.config.js
7└── package.json

javascript

1// vite.config.js
2import { defineConfig } from 'vite'
3
4export default defineConfig({
5  root: 'app',  // Vite looks for index.html in ./app/
6  build: {
7    outDir: '../dist'  // Output relative to root
8  }
9})

Fix 5: Pure Rollup Configuration

If you are using Rollup directly (not through Vite):

javascript

1// rollup.config.js
2export default {
3  input: 'src/index.js',  // Required — Rollup has no auto-detection
4  output: {
5    file: 'dist/bundle.js',
6    format: 'esm'
7  }
8}

javascript

1// Multiple inputs
2export default {
3  input: {
4    main: 'src/main.js',
5    utils: 'src/utils.js'
6  },
7  output: {
8    dir: 'dist',
9    format: 'esm'
10  }
11}

Common Project Structures

Single-Page App (SPA)

1project/
2├── index.html              ← Vite finds this automatically
3├── src/
4│   ├── main.js
5│   └── App.vue
6├── vite.config.js
7└── package.json

No extra configuration needed — Vite finds index.html in the root.

Library

1project/
2├── src/
3│   ├── index.js            ← Library entry
4│   └── components/
5├── vite.config.js          ← Must configure build.lib
6└── package.json

Requires build.lib.entry in vite.config.js.

Monorepo Package

1packages/
2├── ui-library/
3│   ├── src/index.ts
4│   ├── vite.config.ts      ← Must configure build.lib or rollupOptions.input
5│   └── package.json
6└── web-app/
7    ├── index.html
8    ├── vite.config.ts       ← Works automatically
9    └── package.json

Common Pitfalls

Missing index.html in root directory: Vite requires index.html in the root (or the root option directory) for application mode. If you moved it to public/ or src/, either move it back or set root accordingly.
index.html without <script type="module">: An index.html that only has regular <script> tags (not type="module") does not provide Vite an entry point. Add type="module" to your script tag.
Using build.lib and rollupOptions.input simultaneously: When both are specified, they can conflict. In library mode, use build.lib.entry for the entry point. rollupOptions.input is for application mode or overriding specific Rollup behavior.
Relative paths in rollupOptions.input: Always use resolve(__dirname, 'path') for entry points. Relative paths resolve from the working directory, which may differ between development and CI environments.
Vite config in wrong location: vite.config.js must be in the project root (next to package.json). If it is in a subdirectory, Vite will not find it and uses defaults, which may not locate your index.html.

Summary

Vite auto-detects entry points from index.html in the project root — the error means it could not find one
For standard apps, ensure index.html exists at the root with a <script type="module"> tag
For libraries, configure build.lib.entry in vite.config.js
For custom structures, set rollupOptions.input or the root option
For multi-page apps, pass an object to rollupOptions.input with named entries
Always use resolve(__dirname, 'path') for absolute entry point paths

Could not auto-determine entry point from rollupOptions

Master System Design with Codemia

Introduction

The Error

How Vite Determines the Entry Point

Fix 1: Add index.html (Standard Vite App)

Fix 2: Specify rollupOptions.input (Custom Entry)

Multiple Entry Points (Multi-Page App)

Fix 3: Configure build.lib (Library Mode)

Fix 4: Set the root Option

Fix 5: Pure Rollup Configuration

Common Project Structures

Single-Page App (SPA)

Library

Monorepo Package

Common Pitfalls

Summary

Fix 1: Add `index.html` (Standard Vite App)

Fix 2: Specify `rollupOptions.input` (Custom Entry)

Fix 3: Configure `build.lib` (Library Mode)

Fix 4: Set the `root` Option