Rollup
ES module bundler optimized for producing small, tree-shaken library bundles in multiple output formats (esm, cjs, iife, umd).
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Runs locally with no network calls. Agents should pin @rollup/plugin-* versions; the plugin ecosystem varies in maintenance quality.
⚡ Reliability
Best When
Publishing a JavaScript library to npm that must ship tree-shakeable ESM alongside CJS fallback with minimal bundle overhead.
Avoid When
You are building a full frontend application with HMR, or your source files are predominantly CommonJS.
Use Cases
- • Bundle a JavaScript or TypeScript library for npm publication with separate esm and cjs output formats in a single rollup.config.js
- • Apply aggressive tree-shaking to eliminate dead code from a dependency-heavy library before shipping
- • Use the Rollup JavaScript API (rollup(), bundle.generate(), bundle.write()) to drive builds programmatically from an agent
- • Split a library into multiple entry points using input object syntax to produce separate chunks per feature
- • Integrate @rollup/plugin-node-resolve and @rollup/plugin-commonjs to consume npm packages inside an ESM-native bundle
Not For
- • Application bundling with complex dev-server HMR needs — Vite wraps Rollup for this purpose and is a better choice
- • CommonJS-first projects that have not migrated to ESM — Rollup's native model is ES modules and CJS interop adds friction
- • Projects requiring fast TypeScript type-checking at build time — Rollup transpiles but does not type-check
Interface
Authentication
Local build tool — no authentication needed.
Pricing
Open source under MIT license.
Agent Metadata
Known Gotchas
- ⚠ All external dependencies (e.g., 'react', 'lodash') must be listed in the 'external' option or they will be bundled into the output, bloating library size
- ⚠ output.format must be specified explicitly (esm, cjs, iife, umd); omitting it defaults to 'es' which may not match consumer expectations
- ⚠ Dynamic imports (import()) create code-split chunks by default; agents must set output.inlineDynamicImports:true to get a single-file output if needed
- ⚠ Rollup does not resolve Node built-ins (fs, path) for browser targets without @rollup/plugin-node-resolve and browser:true option
- ⚠ Plugin order matters: plugins are executed in array order for transform hooks but in reverse order for generate hooks, which can cause subtle ordering bugs
Alternatives
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Scores are editorial opinions as of 2026-03-06.