From what I've heard there are two main use cases:

- People use bun as an all-in-one frontend web bundler. Personally, I just use esbuild (and webpack, if I'm working on a system using its module federation, like Jupyterlab). My understanding is bun has a machine-translated port of esbuild (ported to Zig, then to Rust) built into it.

- Claude Code runs on bun.

The second point has to be why Anthropic acquired them.