Why Bun’s native Windows support matters for runtime performance

Runtime performance comparison

Bun delivers a high-performance runtime for developers working on Windows, macOS, and Linux. While Node.js and Deno rely on Google’s V8 engine, Bun utilizes Apple’s JavaScriptCore engine. The Bun runtime uses a Zig-powered wrapper to optimize system-level operations like networking. This architecture creates massive speed differences in common backend tasks. Bun 1.3 handles 2 to 3.5 times more requests per second than Node.js in tests using frameworks like Hono or Express. In synthetic benchmarks, Bun’s HTTP server pushes more than 1 million plaintext requests per second per core, which is roughly 2.5 times the throughput of Express on Node.js 22. Startup times also show a massive gap, as Bun boots APIs in 1.2 milliseconds, beating Node.js cold starts by 37 times. This efficiency helps reduce latency for serverless functions. You should evaluate these numbers before migrating your existing production services.

Integrated tools and features

Bun functions as an all-in-one toolkit to replace Node.js. It combines a runtime, a fast JavaScript bundler, a package manager, and a test runner into a single 40 MB binary. The built-in package manager installs dependencies 20 to 40 times faster than npm or yarn, and the resolver handles the average node_modules tree five times faster than the npm 11 version. Bun 1.3 includes zero-configuration frontend development with built-in hot module replacement and React Fast Refresh support. This allows developers to run HTML files directly while Bun handles JavaScript, CSS, and React transpilation and bundling. Bun 1.3 also includes a unified Bun.SQL API and a built-in Redis client that delivers 7.9 times the performance of the popular redis package. The runtime includes a Jest-compatible test runner that reads describe and it blocks natively. It also provides Bun.password for security and bun test for automated verification. Anthropic’s interest in the runtime supports its use in Claude Code, which leverages Bun’s speed for efficient agent workflows. While the project hits 105,000 stars on GitHub, a stubborn long tail of native-binding packages still misbehaves in the Bun environment.

Windows support and deployment

Bun’s native support for Windows simplifies the development workflow for enterprise teams using Windows 10 or Windows 11. This capability matters for teams choosing between Node.js and Deno, especially when evaluating the performance of Zig-powered runtimes for heavy workloads. Bun 1.4, a ground-up Rust rewrite of the core runtime, arrived in August 2026 to succeed the original Zig codebase. This update follows the 1.0 through 1.3 releases that stabilized the project. Bun also provides a fast native JavaScript bundler that outperforms competitors like esbuild, Parcel 2, Rollup, and Webpack. The bundler’s speed improvements range from 1.75x to 220x based on the specific benchmark. This performance helps reduce infrastructure costs for teams that manage high-traffic applications. To manage resources, Bun 1.3 reduces JavaScript memory usage by 10 to 30 percent in frameworks like Next.js and Elysia. Holding 10,000 concurrent WebSocket connections costs about 35 MB of resident memory in Bun versus around 250 MB in Node. Most Express and Fastify applications run on Bun without any code changes. The 1.4.2 patch released in September 2026 fixed seven issues following the 1.4.1 patch which addressed 202 issues. Developers can install Bun fresh following the instructions at bun.sh. How will Bun maintain this speed as it integrates more deeply with the V8 ecosystem?