tsup vs Rollup: Bundling TypeScript Libraries
Pick tsup for fast, near-zero-config TypeScript library builds powered by esbuild; pick Rollup when you need precise control over output, plugins, and tree-shaking for a published package.
tsup and Rollup both bundle TypeScript/JavaScript libraries, but at different abstraction levels. tsup is a thin, opinionated wrapper around esbuild (with rollup-based .d.ts generation) that produces ESM/CJS bundles with minimal config. Rollup is a lower-level, highly configurable bundler known for clean output and strong tree-shaking, widely used to ship libraries.
| tsup | Rollup | |
|---|---|---|
| Engine | esbuild (+ rollup for types) | Rollup core |
| Config | Minimal (tsup.config.ts) | Explicit (rollup.config.js + plugins) |
| Speed | Very fast (esbuild) | Fast, slower than esbuild |
| Output formats | ESM, CJS, IIFE | ESM, CJS, UMD, IIFE, etc. |
| Type declarations | Built in (--dts) | Via plugin (e.g. rollup-plugin-dts) |
| Control | Opinionated | Fine-grained |
Where each genuinely wins
tsup wins on speed and ergonomics: one command produces dual ESM/CJS plus type declarations, which covers most npm libraries with almost no config. Rollup wins when you need exact control, such as custom output naming, advanced code-splitting, specific plugin behavior, or maximum tree-shaking quality, and you are willing to maintain a config and plugin chain.
In CI
tsup keeps build steps short and fast on runners, which lowers per-minute cost. Rollup builds are still fast but configuration-heavy; cache node_modules and the build output so CI does not rebuild unchanged packages. For libraries, run a type check (tsc --noEmit) alongside the bundle in CI, since esbuild does not type-check.
Honest caveats
tsup uses esbuild, which is extremely fast but does not type-check and supports a subset of edge-case transforms; you handle types separately. Rollup gives more control at the cost of more setup and slower builds. Note tsup itself depends on esbuild and Rollup under the hood, so the choice is really about how much control you want.
The verdict
Use tsup for fast, low-config library builds that cover the common ESM/CJS plus types case. Use Rollup when output control, advanced plugins, or tree-shaking quality justify the extra configuration.