rsnext/errors/react-hydration-error.mdx

---
title: Text content does not match server-rendered HTML
---

## Why This Error Occurred

While rendering your application, there was a difference between the React tree that was pre-rendered from the server and the React tree that was rendered during the first render in the browser (hydration).

[Hydration](https://react.dev/reference/react-dom/client/hydrateRoot) is when React converts the pre-rendered HTML from the server into a fully interactive application by attaching event handlers.

### Common Causes

Hydration errors can occur from:

1. Incorrect nesting of HTML tags
   1. `<p>` nested in another `<p>` tag
   2. `<div>` nested in a `<p>` tag
   3. `<ul>` or `<ol>` nested in a `<p>` tag
   4. [Interactive Content](https://html.spec.whatwg.org/#interactive-content-2) cannot be nested (`<a>` nested in a `<a>` tag, `<button>` nested in a `<button>` tag, etc.)
2. Using checks like `typeof window !== 'undefined'` in your rendering logic
3. Using browser-only APIs like `window` or `localStorage` in your rendering logic
4. Using time-dependent APIs such as the `Date()` constructor in your rendering logic
5. [Browser extensions](https://github.com/facebook/react/issues/24430) modifying the HTML
6. Incorrectly configured [CSS-in-JS libraries](https://nextjs.org/docs/app/building-your-application/styling/css-in-js)
   1. Ensure your code is following [our official examples](https://github.com/vercel/next.js/tree/canary/examples)
7. Incorrectly configured Edge/CDN that attempts to modify the html response, such as Cloudflare [Auto Minify](https://developers.cloudflare.com/speed/optimization/content/auto-minify/)

## Possible Ways to Fix It

The following strategies can help address this error:

### Solution 1: Using `useEffect` to run on the client only

Ensure that the component renders the same content server-side as it does during the initial client-side render to prevent a hydration mismatch. You can intentionally render different content on the client with the `useEffect` hook.

```jsx
import { useState, useEffect } from 'react'

export default function App() {
  const [isClient, setIsClient] = useState(false)

  useEffect(() => {
    setIsClient(true)
  }, [])

  return <h1>{isClient ? 'This is never prerendered' : 'Prerendered'}</h1>
}
```

During React hydration, `useEffect` is called. This means browser APIs like `window` are available to use without hydration mismatches.

### Solution 2: Disabling SSR on specific components

Next.js allows you to [disable prerendering](https://nextjs.org/docs/app/building-your-application/optimizing/lazy-loading#skipping-ssr) on specific components, which can prevent hydration mismatches.

```jsx
import dynamic from 'next/dynamic'

const NoSSR = dynamic(() => import('../components/no-ssr'), { ssr: false })

export default function Page() {
  return (
    <div>
      <NoSSR />
    </div>
  )
}
```

### Solution 3: Using `suppressHydrationWarning`

Sometimes content will inevitably differ between the server and client, such as a timestamp. You can silence the hydration mismatch warning by adding `suppressHydrationWarning={true}` to the element.

```jsx
<time datetime="2016-10-25" suppressHydrationWarning />
```

## Common iOS issues

iOS attempts to detect phone numbers, email addresses, and other data in text content and convert them into links, leading to hydration mismatches.

This can be disabled with the following `meta` tag:

```jsx
<meta
  name="format-detection"
  content="telephone=no, date=no, email=no, address=no"
/>
```