webpack vs Rollup: Which Bundler for CI Builds?
webpack is the heavyweight app bundler with a vast loader/plugin ecosystem; Rollup is leaner and favored for tree-shaken library output.
webpack is a mature, highly configurable bundler built for complex applications, with loaders, code-splitting, and a huge plugin ecosystem. Rollup focuses on clean, tree-shaken output and is the common choice for publishing libraries.
| webpack | Rollup | |
|---|---|---|
| Best for | Complex apps | Libraries, lean output |
| Config complexity | Higher | Lower |
| Tree-shaking | Good | Excellent |
| Plugin/loader ecosystem | Largest | Large, mature |
| Code-splitting | Mature, flexible | Supported |
In CI
webpack handles complex application builds - many entry points, advanced code-splitting, and loaders for every asset type - at the cost of heavier config and slower builds. Rollup produces smaller, well tree-shaken bundles with simpler config, which is why it is the go-to for libraries (and the engine behind Vite's production builds). Choose by output target: app vs library.
Speed it up
Cache the build and dependencies keyed on your lockfile, and use persistent caching where supported. Both run on CI runners; faster managed runners cut the wall-clock time of heavy webpack builds.
The verdict
Bundling a complex app with many asset types and split points: webpack. Publishing a library or wanting lean, tree-shaken output: Rollup. Many teams get Rollup's output automatically via Vite.