Docs say Next.js runtime is not supported for middleware, but it works

[hdodov]

Summary

The Next.js docs say:

Middleware currently only supports the Edge runtime. The Node.js runtime can not be used.

…however, I can add the following middleware.ts:

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

export function middleware(request: NextRequest) {
	if (request.nextUrl.pathname.startsWith("/foo")) {
		return NextResponse.redirect(new URL("/bar", request.url));
	}
}

…and when I run npm run dev and open http://localhost:3000/foo it redirects me as expected.

Am I missing something or the docs are misleading?

Additional information

Operating System:
  Platform: darwin
  Arch: x64
  Version: Darwin Kernel Version 23.6.0: Mon Jul 29 21:13:00 PDT 2024; root:xnu-10063.141.2~1/RELEASE_X86_64
  Available memory (MB): 32768
  Available CPU cores: 16
Binaries:
  Node: 20.16.0
  npm: 10.8.1
  Yarn: 1.22.19
  pnpm: 9.8.0
Relevant Packages:
  next: 14.2.5
  eslint-config-next: 14.2.5
  react: 18.3.1
  react-dom: 18.3.1
  typescript: 5.5.4
Next.js Config:
  output: N/A

Example

No response

[Juneezee]

Your code works because you are not using any Node.js APIs that are not available in the Edge Runtime. See the Unsupported APIs section of Edge Runtime ¹.

Footnotes

1. https://nextjs.org/docs/app/api-reference/edge#unsupported-apis ↩

[hdodov]

But the docs don't mention anything about support, nor APIs…

When I read this:

The Node.js runtime can not be used.

…I understand that middleware can not be used when running Next.js in Node.

This would be infinitely clearer:

Middleware currently only supports APIs compatible with the Edge runtime. APIs exclusive to Node.js are unsupported.