# Deploy a Bun application on Vercel

[Vercel](https://vercel.com/) is a cloud platform for building, deploying, and scaling apps.

<Warning>
  The Bun runtime is in Beta. Some features are not yet supported — for example, automatic source maps, byte-code
  caching, and metrics on `node:http/https`.
</Warning>

<Note>
  `Bun.serve` is not supported on Vercel Functions. Use Bun with frameworks supported by Vercel, like Next.js, Express,
  Hono, or Nitro.
</Note>

---

<Steps>
	<Step title="Configure Bun in vercel.json">
		To enable the Bun runtime for your Functions, add a `bunVersion` field in your `vercel.json` file:

    	```json vercel.json icon="file-json"
    	{
    		"bunVersion": "1.x" // [!code ++]
    	}
    	```

    	Vercel automatically detects this configuration and runs your application on Bun. The value must be `"1.x"`; Vercel handles the minor version internally.

    	For best results, match your local Bun version with the version used by Vercel.
    </Step>

    <Step title="Next.js configuration">
    	If you’re deploying a **Next.js** project (including ISR), update your `package.json` scripts to use the Bun runtime:

    	```json package.json icon="file-json"
    	{
    		"scripts": {
    			"dev": "bun --bun next dev", // [!code ++]
    			"build": "bun --bun next build" // [!code ++]
    		}
    	}
    	```

    	<Note>
    		The `--bun` flag runs the Next.js CLI under Bun. Bundling (with Turbopack or Webpack) is unchanged.
    	</Note>

    	With these scripts, both local development and builds use Bun.
    </Step>

    <Step title="Deploy your app">
    	Connect your repository to Vercel, or deploy from the CLI:

    	```bash terminal icon="terminal"
    	# Using bunx (no global install)
    	bunx vercel login
    	bunx vercel deploy
    	```

    	Or install the Vercel CLI globally:

    	```bash terminal icon="terminal"
    	bun i -g vercel
    	vercel login
    	vercel deploy
    	```

    	[Learn more in the Vercel Deploy CLI documentation →](https://vercel.com/docs/cli/deploy)
    </Step>

    <Step title="Verify the runtime">
    	To confirm your deployment uses Bun, log the Bun version:

    	```ts index.ts icon="/icons/typescript.svg"
    	console.log("runtime", process.versions.bun);
    	```
    	```txt
    	runtime 1.3.3
    	```

    	[See the Vercel Bun Runtime documentation for feature support →](https://vercel.com/docs/functions/runtimes/bun#feature-support)
    </Step>

</Steps>

---

- [Fluid compute](https://vercel.com/docs/fluid-compute): Both Bun and Node.js runtimes run on Fluid compute and support the same core Vercel Functions features.
- [Middleware](https://vercel.com/docs/routing-middleware): To run Routing Middleware with Bun, set the runtime to `nodejs`:

```ts middleware.ts icon="/icons/typescript.svg"
export const config = { runtime: "nodejs" }; // [!code ++]
```