How to Fix React Hydration Error in Nextjs - Practical Guide
Tags: webdev, javascript, beginners, react
Published: 2023-02-24 14:19:13

Are you struggling with the React Hydration Error in Nextjs? Don't worry; you're not alone! Many developers face this error when rendering their React components on the server and client sides. It can be frustrating, but fear not; we've got you covered.

This is a standard error; you might find a solution online, but I tried most of them, but it didn't work for me. This article will provide a simple and practical guide on fixing the React Hydration Error in Nextjs with examples of my errors and how I set them.

Whether you're a beginner or an experienced developer, this guide will help you understand the error's causes and provide practical solutions to fix it.

So, let's dive in and solve this problem once and for all!

## Understanding React Hydration

It's essential to understand React hydration as a developer who wants to build efficient and reliable web applications using React and Nextjs.

### What is a React Hydration?

The React hydration process involves attaching event handlers and states to the server-side markup during Server-Side Rendering (SSR). As a page loads, React reconciles the server-generated markup with the client-side markup and attaches event handlers and states.

The web application must behave correctly and interact with the end user during this process. The application might throw an error if the React Hydration process fails or behave unexpectedly if the operation fails.

Therefore, it's crucial to understand how React Hydration works and how to fix any issues that arise during the process.

### Causes of React Hydration Error in Nextjs

React Hydration Errors in Nextjs can be caused by **inconsistencies between server and client-rendered markup** and **mismatched component states**.

When the markup generated on the server side differs from what is generated on the client side, or when the state of a component on the server side doesn't match the state on the client side, the application can throw errors or behave unexpectedly.

Identifying and fixing these issues can be challenging, but understanding their causes is essential to improving web application performance and reliability.

## A Practical Guide to Fix React Hydration Error in Nextjs

![Fix React Hydration Error in Nextjs](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/k4kiy7yho3l4rb4ithk1.png)

There are a couple of ways to fix the Reactjs hydration error, but I will share the standard and the hydration error I encountered while working on this decentralized identity project.

### Error 🪲

I needed to check if the browser window had a valid `ethereum` object.

```javascript
{connection.status === "connected" ? (
            
    {/* condition when its connected*/}
                  
    ) : typeof window !== "undefined" && "ethereum" in window ? (
                       
    {/* condition when ethereum is available */}

    ) : (
 
    <p>
     An injected Ethereum provider such as MetaMask
    </p>
)}
```

### How to Fix It 🛠️

In the problem above, adding `typeof window !== "undefined"` caused the hydration error, which occurs if the server-rendered HTML does not match the client-rendered HTML.

Here's an example of how you can modify the code to avoid a hydration error:

```javascript
import { useEffect, useState } from 'react';

function MyComponent() {
  const [isEthereumAvailable, setIsEthereumAvailable] =     useState(false);

  useEffect(() => {
    if (typeof window !== 'undefined' && 'ethereum' in window) {
      setIsEthereumAvailable(true);
    }
  }, []);

  return (
    <>
    {connection.status === "connected" ? (
            
        {/* condition when its connected*/}
      ) : isEthereumAvailable ? (
       
        {/* condition when ethereum is available */}

      ) : (
       {/* condition when ethereum is not available */}
      )
    }
    </>
  );
}
```

### Error 🪲

```javascript
{connection.status === "connected" && record && record.content && (
    <div>
        {/* condition when ethereum is not available */}
    </div>
     ) : (
    <p>No profile found.</p>
)}
```

In the code snippet above, `connection` and `record` is an object; meanwhile, the record is fetched asynchronously, leading to hydration.

### How to Fix It 🛠️

```javascript
{connection.status === "connected" && record && record.content ? (
    <div>
        {/* condition when ethereum is not available */}
    </div>
     ) : (
    <p>No profile found.</p>
)}
```

`record.content` It is fetched asynchronously and can differ between the server and client rendering; the initial server-rendered HTML may not match the client-rendered HTML. Changing the last `&&` operator to a ternary `?` fixed the problem.

I hope you find this helpful post and fix any React hydration error within 3 minutes.

## Conclusion

In conclusion, this post teaches us how a hydration error can occur in Next.js when the server-rendered HTML output doesn't match the client-rendered HTML output. This can happen when client-side-only code, such as code that depends on the window object, is executed during server rendering.

Additionally, you can ensure that the data used to render your components is consistent between the server and client, especially when the data is asynchronously fetched.

By following these best practices, you can ensure that your Next.js application renders correctly without any hydration errors. Always test your application thoroughly to catch any issues before deploying to production.

## Reference

* [Nextjs React Hydration Error](https://nextjs.org/docs/messages/react-hydration-error)
    
* [Fix Next.js "Text content does not match server-rendered HTML.](https://www.netlify.com/blog/fix-next-js-react-hydration-error/)"
    


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