What is a Hydration Error in Next.js 13+?

A hydration error happens when the HTML that is sent from the server doesn’t exactly match what React expects on the client. This mismatch causes the app to “break” when trying to connect the two.

🌊 In Simple Terms:

The server gives your browser a static HTML page, and React tries to make it interactive. If what the browser sees isn’t the same as what React expects, the hydration fails!

⚠️ Common Causes

  • Using Math.random() or Date.now() directly
  • Client-only browser APIs rendered on the server
  • Differences in rendering logic (e.g., screen size)

✅ How to Fix It

  • Move dynamic code into useEffect()
  • Use "use client" for interactive components
  • Avoid rendering browser-only logic on the server