What I learned fixing hydration errors in my nextjs project

Let me set the scene: I’m building a learning management system with Next.js, using app/ directory structure, server components, client components, and a bunch of state handling. You know, the usual soup of modern React. What was supposed to be a productive Sunday turned into a full-on battle with hydration errors.

This blog is part vent, part lesson, and 100% real. If you're dealing with hydration errors in Next.js, especially when juggling layouts, auth, and dynamic content, I got you.

What’s a Hydration Error?

In React (and by extension Next.js), hydration is the process where React takes the server-rendered HTML and makes it interactive on the client. If the content rendered on the server doesn’t match what React expects on the client – boom 💥 – hydration mismatch error.

Next.js will yell at you with something like:

Hydration failed because the initial UI does not match what was rendered on the server.

Where It Went Wrong?

Here are few problems that faced. “NOT ALL” 😄

Problem 1

<SidebarLayout>
  <UserHeader />  // shows avatar if logged in
  {children}
</SidebarLayout>

Problem:The avatar depends on the auth state from Redux or NextAuth session. On the server, that info might not be ready. So the server rendered “Sign in” while the client had “Welcome, Savita!” → mismatch.

Fix: Delay Rendering Until Auth Is Ready

I wrapped my layout in something like:

"use client"

import { useSession } from "next-auth/react"

const AuthWrapper = ({ children }) => {
  const { status } = useSession()

  if (status === "loading") return null
  return <>{children}</>
}

This helped by waiting for the auth state before rendering UI that depended on it. No mismatch = no hydration error.

---

Problem 2

Server Components Rendering Client Components

Next.js loves server components, but you can’t mix client logic randomly.

I had something like:

// Server component
const Dashboard = () => {
  return (
    <>
      <ClientOnlyStats /> // uses useEffect, charts, etc.
    </>
  )
}

Oops. ClientOnlyStats was relying on window, user data from Redux, and client only effects. That’s a recipe for hydration mismatch.

Fix: Wrap in use client or isolate to its own component

// ClientOnlyStats.tsx
'use client'

const ClientOnlyStats = () => {
  // Safe to use window, hooks, etc.
}

Or even better, I used a ClientWrapper component in places where I had multiple client-only pieces.

---

Problem: 3

Redux vs Server Rendering

Using Redux in layouts or pages that render on the server side = potential mismatch. Why? The store might initialize differently on the server vs client.

Fix: Hydrate Redux Properly

Use something like:

// _app.tsx or layout.tsx
<Provider store={store}>
  <HydrateRedux>{children}</HydrateRedux>
</Provider>

And make sure initial state is same across server and client. Or move critical parts of the UI to client only wrappers.

---

Final Note

• Hydration errors = mismatch between server HTML and client expectations

• Delay rendering or wrap conditionals in useEffect/useSession checks

• Don't assume auth state is ready on server unless you're doing SSR properly

• Split client logic into clean, isolated components with "use client"

• Think of what your server renders as static HTML – and then see what might break when React takes over

Conclusion

I didn’t finish the whole LMS page that day, but I came out a little wiser. Next.js is powerful, but hydration errors can creep in so easily, especially when working with auth, layouts, and dynamic client state.

If you're working on something similar and pulling your hair out, just know you're not alone. These errors suck, but they can be debugged, one step at a time.

Let me know if you're also building an something or struggling with hydration stuff — would love to swap war stories.