Run Bun

The playground runs a Bun project entirely in your browser:

• Bun’s own code, compiled to wasm64. The transpiler, bundler and semver come from Bun’s Rust crates that don’t depend on JavaScriptCore, built for 64-bit WebAssembly (Memory64).
• JS shims for the runtime. Bun.*, bun:* and node:* APIs are implemented in JavaScript on top of the browser’s engine.
• A virtual file system. Your project lives in memory and is saved to the browser’s storage.
• A service worker serves your modules and the preview of Bun.serve and node:http servers.

Try it: this server runs in your browser when you click Run.

index.ts

const server = Bun.serve({
  routes: {
    "/": () => new Response("<h1>Hello from Bun.serve</h1><a href='/api/time'>/api/time</a>", { headers: { "content-type": "text/html" } }),
    "/api/time": () => Response.json({ now: new Date().toISOString(), bun: Bun.version }),
  },
});

console.log(`Listening on ${server.url}`);

Because the runtime is a set of shims, not every Bun or Node API is there yet. Check Compatibility before porting a project, and the Features tour for what the playground can do.