Yarn vs Bun

The problem with Yarn

#

I’ve been using Yarn for a while — both locally and in CI/CD workflows. It works, but two things kept bugging me:

• Slow installs in CI — even with caching, yarn install was consistently the longest step in my pipelines. On a medium-sized project it could easily eat 40-60 seconds, sometimes more.
• Dependency resolution quirks — every now and then Yarn would get confused with peer dependencies or produce slightly different lockfile results across environments. Nothing catastrophic, but enough to waste time debugging.

Giving Bun a chance

#

Bun isn’t as mature as Yarn or npm. It’s younger, the ecosystem around it is still growing, and I had my doubts. But the promise of a faster package manager written in Zig with native-speed installs was too tempting to ignore.

So I swapped yarn install for bun install in a few pipelines and ran them side by side for a couple of weeks.

What I found

#

The difference was immediate. Bun claims up to 25x faster installs compared to npm, and while real-world numbers depend on the project, I consistently saw 3-5x improvement over Yarn in my workflows.

A few things that stood out:

• Install times dropped significantly — what took Yarn 45+ seconds now finishes in under 15 with Bun. In CI, that adds up fast.
• Zero dependency issues — I expected at least some edge cases, but bun install resolved everything correctly every single time. No phantom dependency problems, no lockfile drift.
• Drop-in replacement — Bun reads package.json the same way, supports workspaces, overrides, and even migrates from other lockfiles automatically. Switching required almost no config changes.
• bun ci for reproducible builds — equivalent to --frozen-lockfile, it fails if package.json is out of sync with bun.lock. Exactly what you want in a pipeline.

The maturity question

#

Is Bun production-ready as a package manager? Based on my experience — yes. The runtime side of Bun (replacing Node.js) is a different conversation, but as a package manager it’s been rock-solid. It handles everything I’ve thrown at it without issues.

The bun.lock format switched from binary to a human-readable text format in Bun 1.2, which makes diffs and code reviews much easier. Lifecycle scripts are sandboxed by default (they don’t run unless you explicitly trust a package), which is a nice security bonus.

Verdict

#

I went in skeptical and came out convinced. Bun as a package manager is fast, reliable, and worth using in production pipelines. If your CI spends too much time on yarn install, give bun install a try — you might be surprised.