Deploy a Bun application on Vercel
Vercel is a cloud platform that lets you build, deploy, and scale your apps.
The Bun runtime is in Beta; certain features (e.g., automatic source maps, byte-code caching, metrics on
node:http/https) are not yet supported.
Bun.serve is currently not supported on Vercel Functions. Use Bun with frameworks supported by Vercel, like Next.js,
Express, Hono, or Nitro.
Configure Bun in vercel.json
To enable the Bun runtime for your Functions, add a bunVersion field in your vercel.json file:
{
"bunVersion": "1.x"
}Vercel automatically detects this configuration and runs your application on Bun. The value has to be "1.x", Vercel handles the minor version internally.
For best results, match your local Bun version with the version used by Vercel.
Next.js configuration
If you’re deploying a Next.js project (including ISR), update your package.json scripts to use the Bun runtime:
{
"scripts": {
"dev": "bun --bun next dev",
"build": "bun --bun next build"
}
}The --bun flag runs the Next.js CLI under Bun. Bundling (via Turbopack or Webpack) remains unchanged, but all commands execute within the Bun runtime.
This ensures both local development and builds use Bun.
Deploy your app
Connect your repository to Vercel, or deploy from the CLI:
# Using bunx (no global install)
$ bunx vercel login
$ bunx vercel deployOr install the Vercel CLI globally:
$ bun i -g vercel
$ vercel login
$ vercel deployVerify the runtime
To confirm your deployment uses Bun, log the Bun version:
console.log("runtime", process.versions.bun);
// => runtime 1.3.5See the Vercel Bun Runtime documentation for feature support →
- Fluid compute: Both Bun and Node.js runtimes run on Fluid compute and support the same core Vercel Functions features.
- Middleware: To run Routing Middleware with Bun, set the runtime to
nodejs:
export const config = { runtime: "nodejs" };