Bun Next.js

Run Next.js applications with Bun for faster development and builds.

Quick Start

# Create new Next.js project with Bun
bunx create-next-app@latest my-app
cd my-app

# Install dependencies
bun install

# Development
bun run dev

# Build
bun run build

# Production
bun run start

Project Setup

package.json

{
  "scripts": {
    "dev": "next dev --turbo",
    "build": "next build",
    "start": "next start",
    "lint": "next lint"
  },
  "dependencies": {
    "next": "^16.1.1",
    "react": "^19.2.3",
    "react-dom": "^19.2.3"
  }
}

Use Bun as Runtime

{
  "scripts": {
    "dev": "bun --bun next dev",
    "build": "bun --bun next build",
    "start": "bun --bun next start"
  }
}

The --bun flag forces Next.js to use Bun's runtime instead of Node.js.

Configuration

next.config.js

/** @type {import('next').NextConfig} */
const nextConfig = {
  // Enable experimental features
  experimental: {
    // Turbopack (faster dev)
    turbo: {},
  },

  // Server-side Bun APIs
  serverExternalPackages: ["bun:sqlite"],

  // Webpack config (if needed)
  webpack: (config, { isServer }) => {
    if (isServer) {
      // Allow Bun-specific imports
      config.externals.push("bun:sqlite", "bun:ffi");
    }
    return config;
  },
};

module.exports = nextConfig;

Using Bun APIs in Next.js

Server Components

// app/page.tsx (Server Component)
import { Database } from "bun:sqlite";

export default async function Home() {
  const db = new Database("data.sqlite");
  const users = db.query("SELECT * FROM users").all();
  db.close();

  return (
    <div>
      {users.map((user) => (
        <p key={user.id}>{user.name}</p>
      ))}
    </div>
  );
}

API Routes

// app/api/users/route.ts
import { Database } from "bun:sqlite";

export async function GET() {
  const db = new Database("data.sqlite");
  const users = db.query("SELECT * FROM users").all();
  db.close();

  return Response.json(users);
}

export async function POST(request: Request) {
  const body = await request.json();

  const db = new Database("data.sqlite");
  db.run("INSERT INTO users (name) VALUES (?)", [body.name]);
  db.close();

  return Response.json({ success: true });
}

File Operations

// app/api/files/route.ts
export async function GET() {
  const file = Bun.file("./data/config.json");
  const config = await file.json();

  return Response.json(config);
}

export async function POST(request: Request) {
  const data = await request.json();
  await Bun.write("./data/config.json", JSON.stringify(data, null, 2));

  return Response.json({ saved: true });
}

Server Actions

// app/actions.ts
"use server";

import { Database } from "bun:sqlite";
import { revalidatePath } from "next/cache";

export async function createUser(formData: FormData) {
  const name = formData.get("name") as string;

  const db = new Database("data.sqlite");
  db.run("INSERT INTO users (name) VALUES (?)", [name]);
  db.close();

  revalidatePath("/users");
}

export async function deleteUser(id: number) {
  const db = new Database("data.sqlite");
  db.run("DELETE FROM users WHERE id = ?", [id]);
  db.close();

  revalidatePath("/users");
}

Middleware

// middleware.ts
import { NextResponse } from "next/server";
import type { NextRequest } from "next/server";

export function middleware(request: NextRequest) {
  // Check auth
  const token = request.cookies.get("token");

  if (!token && request.nextUrl.pathname.startsWith("/dashboard")) {
    return NextResponse.redirect(new URL("/login", request.url));
  }

  return NextResponse.next();
}

export const config = {
  matcher: ["/dashboard/:path*"],
};

Environment Variables

# .env.local
DATABASE_URL=./data.sqlite
API_SECRET=your-secret-key

// Access in server components/actions
const dbUrl = process.env.DATABASE_URL;
const secret = process.env.API_SECRET;

// Expose to client (prefix with NEXT_PUBLIC_)
// .env.local
NEXT_PUBLIC_API_URL=https://api.example.com

Deployment

Build for Production

bun run build
bun run start

Docker

FROM oven/bun:1

WORKDIR /app

COPY package.json bun.lockb ./
RUN bun install --frozen-lockfile

COPY . .
RUN bun run build

EXPOSE 3000

CMD ["bun", "run", "start"]

Vercel

# Install Vercel CLI
bun add -g vercel

# Deploy
vercel

Note: Vercel's edge runtime uses V8, not Bun. Bun APIs work in:

• Server Components (Node.js runtime)
• API Routes (Node.js runtime)
• Server Actions (Node.js runtime)

Performance Tips

1. Use Turbopack for faster dev:

   bun run dev --turbo
   

2. Prefer Server Components - Less JavaScript sent to client

3. Use Bun SQLite instead of external databases for simple apps

4. Enable compression:

   // next.config.js
   module.exports = {
     compress: true,
   };
   

Common Errors

Error	Cause	Fix
Cannot find bun:sqlite	Wrong runtime	Use bun --bun next dev
Module not found	Missing dependency	Run bun install
Hydration mismatch	Server/client diff	Check data fetching
Edge runtime error	Bun API on edge	Use Node.js runtime

When to Load References

Load references/app-router.md when:

• App Router patterns
• Route groups
• Parallel routes

Load references/caching.md when:

• Data caching strategies
• Revalidation patterns
• Static generation