Hydration mismatch React Next.js

Why This Happens

In React, server html doesn't match client-rendered html. This is one of the most common React errors developers encounter. Understanding the root cause helps you fix it quickly and prevent it from recurring.

The Problem

function App() {
  return <p>{Date.now()}</p>;
}

The Fix

'use client';
function App() {
  const [time, setTime] = useState('');
  useEffect(() => setTime(Date.now()), []);
  return <p>{time}</p>;
}

Step-by-Step Fix

1. 1

   Identify the error

   Look at the error message: Hydration failed. This tells you exactly what went wrong.

2. 2

   Find the cause

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

3. 3

   Apply the fix

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