Edge runtime vs Node.js runtime in Next.js

Runtimes in Next.js

Next.js supports two runtimes for server-side code: the default Node.js runtime and the Edge runtime. Each has different capabilities, performance characteristics, and API availability.

Node.js Runtime (Default)

The standard Node.js environment with full access to all Node.js APIs:

tsx

// Default — no config needed
export default async function Page() {
  // Full Node.js API access
  const fs = require("fs");
  const data = fs.readFileSync("./data.json", "utf-8");

  return <div>{data}</div>;
}

Edge Runtime

A lightweight runtime based on Web APIs (similar to Cloudflare Workers). Runs at CDN edge locations for minimal latency:

tsx

// Opt-in to Edge runtime
export const runtime = "edge";

export default function Page() {
  return <div>This runs at the edge!</div>;
}

tsx

// Edge API route
export const runtime = "edge";

export async function GET(request: Request) {
  const { searchParams } = new URL(request.url);
  const name = searchParams.get("name");

  return Response.json({ hello: name });
}

Comparison

Feature	Node.js Runtime	Edge Runtime
Cold start	Slower (~250ms)	Very fast (~1-5ms)
Location	Single region	Edge locations worldwide
Max execution time	No limit (varies by host)	Limited (typically 30s)
Bundle size	No limit	Limited (~1-4MB)
Node.js APIs	✅ Full access	❌ Limited subset
npm packages	✅ All	⚠️ Only Web API-compatible
File system	✅ `fs` module	❌ Not available
Native modules	✅ Yes	❌ No
Streaming	✅ Yes	✅ Yes
Web APIs	✅ Yes	✅ Yes (native)

Middleware (Always Edge)

Next.js Middleware always runs on the Edge runtime:

tsx

// middleware.ts — automatically runs on Edge
import { NextResponse } from "next/server";
import type { NextRequest } from "next/server";

export function middleware(request: NextRequest) {
  // Fast execution at edge location closest to user
  const country = request.geo?.country || "US";

  if (country === "UA") {
    return NextResponse.redirect(new URL("/ua", request.url));
  }

  return NextResponse.next();
}

When to Use Each

Use Node.js Runtime (default)

Database connections (Prisma, Drizzle with native drivers)
File system operations
Heavy computation
Complex npm packages
Long-running operations

Use Edge Runtime

Personalization (geo, A/B testing)
Redirects and rewrites
Authentication token verification
Simple API responses
When latency matters most

The Node.js runtime is the default and supports the full Node.js ecosystem. The Edge runtime is for performance-critical paths that need minimal latency and run close to users. Use Edge for middleware, simple APIs, and personalization. Use Node.js for database access, file operations, and complex logic.

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