The edge runtime does not support Node.js 'crypto' module

Error: The edge runtime does not support Node.js 'crypto' module.
Learn More: https://nextjs.org/docs/messages/node-module-in-edge-runtime

Why it happens

Next.js can run middleware and routes on a lightweight Edge runtime. It doesn't have Node.js APIs such as crypto, fs or child_process. Any package that uses them breaks there, even if it only imports them indirectly.

Next.js changed the defaults recently. In Next.js 15, middleware.ts defaults to Edge, and the Node.js runtime for middleware became stable in 15.5. In Next.js 16, middleware is renamed to proxy.ts, which runs on Node.js by default.

Fix it by hand

1. Find the import. Run next dev: Next.js shows in the console and the browser which file imports the unsupported module.
2. On Next.js 16, rename middleware to proxy with the official codemod. Proxy runs on Node.js, and setting a runtime option in it throws an error, so remove any you had:

   npx @next/codemod@canary middleware-to-proxy .

3. On Next.js 15.5 or later, keep middleware.ts and switch it to Node.js:

   export const config = {
     runtime: 'nodejs',
     matcher: ['/dashboard/:path*'],
   }

4. In a route that sets export const runtime = 'edge', remove that line unless you need Edge. Routes run on Node.js by default.
5. If the code must stay on Edge, replace the Node import. Use the Web Crypto API (crypto.subtle, crypto.getRandomValues) instead of node:crypto, and a JWT library built for Web-interoperable runtimes, such as jose, instead of jsonwebtoken.
6. Run next build locally and confirm the error is gone before you redeploy.

Stop it happening again

• Keep middleware or proxy small: read a cookie, redirect or rewrite. Do database and password work in server code.
• Before adding a package to middleware or an edge route, check that it supports Web APIs only.
• Run next build before every push. The dev server doesn't catch every runtime problem.