Hot reload an HTTP server

The --hot flag runs a file with hot reloading enabled. When any module or file changes, Bun re-runs the file.

$ bun --hot run index.ts

Bun detects when you are running an HTTP server with Bun.serve(). It reloads your fetch handler when source files change, without restarting the bun process. This makes hot reloads nearly instantaneous.

Bun.serve({
  port: 3000,
  fetch(req) {
    return new Response("Hello world");
  },
});