# Feature catalog — rolldown/rolldown

> Canonical page: https://codevetter.com/unpack/rolldown/feature-catalog

# Feature catalog — rolldown/rolldown

Scanned commit 37d60ff510b4b326f4b587c27f28c606d76373e8 (2026-10-02). Generated by codevetter codevetter 1.15.0 on 2026-10-02.

Source inspection; upstream code and tests were not executed.

The user-facing product is chiefly a CLI and a programmatic bundling API. Output operations support memory generation and filesystem writing, complemented by plugins and compiler utilities. Experimental surfaces expose development-engine callbacks, browser memory filesystems, and Vite-oriented integrations. The following catalog covers inspected capabilities rather than asserting an exhaustive option inventory.
- rolldown(input) returns a Rollup-compatible bundle object whose generate() produces in-memory output and write() produces disk output. — [packages/rolldown/src/api/rolldown/index.ts#L6-12](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/api/rolldown/index.ts#L6-L12) [packages/rolldown/src/api/rolldown/rolldown-build.ts#L45-69](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/api/rolldown/rolldown-build.ts#L45-L69)
- The experimental build() convenience API defaults write to true, supports write:false, accepts arrays, and closes each individual build in finally. — [packages/rolldown/src/api/build.ts#L12-19](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/api/build.ts#L12-L19) [packages/rolldown/src/api/build.ts#L55-71](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/api/build.ts#L55-L71)
- The CLI handles help/version, config-based or positional-input bundling, and --environment assignments; without an output destination it prints generated code/assets, while watch requires an output destination. — [packages/rolldown/src/cli/index.ts#L17-54](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/cli/index.ts#L17-L54) [packages/rolldown/src/cli/commands/bundle.ts#L46-75](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/cli/commands/bundle.ts#L46-L75)
- Configuration discovery supports rolldown.config with .js/.mjs/.cjs/.ts/.mts/.cts extensions; config functions receive raw CLI arguments, and native versus bundle loaders select execution paths. — [packages/rolldown/src/utils/load-config.ts#L62-74](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/utils/load-config.ts#L62-L74) [packages/rolldown/src/utils/load-config.ts#L165-185](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/utils/load-config.ts#L165-L185) [packages/rolldown/src/cli/commands/bundle.ts#L25-42](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/cli/commands/bundle.ts#L25-L42)
- watch() rebuilds when modules change and exposes event/change/restart/close notifications; BUNDLE_END and ERROR events carry results with close support. — [packages/rolldown/src/api/watch/index.ts#L9-16](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/api/watch/index.ts#L9-L16) [packages/rolldown/src/api/watch/watcher.ts#L19-59](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/api/watch/watcher.ts#L19-L59)
- Experimental DevEngine exposes a current module graph, HMR/output/additional-asset callbacks, rebuild strategy selection, and configurable polling/debounce/include/exclude watch settings. — [packages/rolldown/src/api/dev/dev-engine.ts#L34-58](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/api/dev/dev-engine.ts#L34-L58) [packages/rolldown/src/api/dev/dev-engine.ts#L76-134](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/api/dev/dev-engine.ts#L76-L134)
- rolldown/utils exports synchronous/asynchronous parsing, minification, and transformation plus TsconfigCache and Visitor; experimental browser builds additionally expose memfs. — [packages/rolldown/src/utils-index.ts#L1-13](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/utils-index.ts#L1-L13) [packages/rolldown/src/experimental-index.ts#L58-88](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/experimental-index.ts#L58-L88)
- Inspected builtins cover external-require conversion and replacement, plus experimental Vite resolve/JSON/glob/import-analysis/preload/worker/React-refresh/reporting/manifest/transform helpers and bundle analysis. — [packages/rolldown/src/plugins-index.ts#L1-2](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/plugins-index.ts#L1-L2) [packages/rolldown/src/experimental-index.ts#L24-54](https://github.com/rolldown/rolldown/blob/37d60ff510b4b326f4b587c27f28c606d76373e8/packages/rolldown/src/experimental-index.ts#L24-L54)

Every claim links to its cited files at the pinned commit. Citations identify source evidence; they do not establish runtime correctness. Independent CodeVetter scan — not reviewed by upstream maintainers.

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