Bun Development Server Setup

Set up high-performance development servers using Bun.serve with built-in HMR, React Fast Refresh, and native Bun 1.4 features.

What's new in Bun 1.4

Built-in HMR: bun run --hot handles HMR natively — no custom WebSocket code needed
routes in Bun.serve (1.2.16): Declarative file-based routing for static files
HTTP/2 support: Bun.serve({ http: { ... } }) for HTTP/2 with TLS
Backpressure: ReadableStream request/response bodies auto-pause when sockets fill
WebSocket.pause()/resume() (1.4.1): Control WebSocket message flow
Bun.Terminal (1.3.5, improved 1.4.0): Built-in PTY for driving terminal apps
50% faster startup on Windows, lower memory usage
Native streams: ReadableStream/WritableStream up to 7× faster