Edge Runtime unsupported API Next.js middleware

Why This Happens

In Next.js, middleware runs on edge runtime which has limited apis. This is one of the most common Next.js errors developers encounter. Understanding the root cause helps you fix it quickly and prevent it from recurring.

The Problem

// middleware.ts
import fs from 'fs';  // Not available!

The Fix

// Use only Web APIs in middleware
// fs, path, etc. are not available

Step-by-Step Fix

1. 1

   Identify the error

   Look at the error message: Middleware error: Edge Runtime does not support. This tells you exactly what went wrong.

2. 2

   Find the cause

   Check the stack trace to find which line of your Next.js code triggered this error.

3. 3

   Apply the fix

   Use the corrected code pattern shown above. Test to confirm the error is resolved.