NetworkError when attempting to fetch resource in Next.js: Causes and How to Fix

Check Your Network Configuration

• Ensure that your network settings are configured correctly. Incorrect DNS settings, firewall restrictions, or proxy settings could block network traffic, causing a `NetworkError`.

 

• Verify if you are using a VPN or restricted network environment that might affect your application's network requests.

Enable CORS in Your API

• Cross-Origin Resource Sharing (CORS) might be blocking your requests. Make sure that your API server includes the correct `Access-Control-Allow-Origin` headers.

 

• If using a Node.js server with Express, you can use the `cors` middleware:

const express = require('express');
const cors = require('cors');
const app = express();

app.use(cors());

Use Environment Variables for API URLs

• Hardcoding URLs can lead to issues if the API endpoints change. Use environment variables to manage API URLs.

 

• Create a `.env.local` file in your Next.js project root:

NEXT_PUBLIC_API_BASE_URL=https://yourapi.com

• Access this variable in your component or API fetch logic:

const apiUrl = process.env.NEXT_PUBLIC_API_BASE_URL;
fetch(`${apiUrl}/endpoint`)
  .then(response => response.json())
  .then(data => console.log(data))
  .catch(error => console.error('Error:', error));

Check Fetch Syntax and Network Requests

• Inspect the syntax used in your `fetch` requests. Ensure you are using correct methods, headers, body formats, etc.

 

• Utilize browser development tools to inspect network requests. Check for failed requests and the associated error messages or status codes.

Handle Server-side and Client-side Fetching Appropriately

• In Next.js, determine if your fetch operation should occur on the server-side (using `getServerSideProps` or `getStaticProps`) or client-side (inside React components).

 

• Server-side fetching can prevent some network errors when pre-rendering pages:

export async function getServerSideProps(context) {
  try {
    const res = await fetch('https://yourapi.com/data');
    const data = await res.json();

    return { props: { data } };
  } catch (err) {
    console.error('Failed to fetch data:', err);
    return { props: { data: null } };
  }
}

Update and Verify Dependencies

• Outdated or improperly installed dependencies can cause network errors. Ensure all your npm packages and the Node.js environment are updated.

 

• Run:

npm update

• Check if dependency-related errors persist after updates.