Next.js Disabling ETag Generation

The problem with not using ETags is that, without them, the client has no way of knowing whether the content cached is still up-to-date. This can result in the client making unnecessary requests to the server, even when the content has not changed. This can lead to slower page load times, higher network usage, and increased server load.

ETags (Entity tags) are used in Next.js to improve performance and reduce unnecessary data transfers between the client and the server. ETags allow the server to verify whether the client’s cached resources are up-to-date or not, and if they are, it can avoid sending the same data again. This can significantly reduce the number of requests that need to be made and the amount of data that needs to be transferred, thereby improving the overall performance of your Next.js application.

What are ETags? 

ETags are a mechanism used by web servers to validate cached responses. When a user requests a page, the server generates an ETag, which is a unique identifier for that page. If the user requests the same page again, the browser can send the ETag to the server to check if the page has been modified. If the page has not been modified, the server can respond with a 304 Not Modified status code, which tells the browser to use the cached version of the page.

Approaches for why disablement:

1. The caching Issues
2. The partition over the cluster is not properly synced.

Why disable ETag generation?

There are several reasons why you might want to disable ETag generation in Next.js. For example, if you’re using a caching layer such as Varnish or Cloudflare, ETags may not be necessary. Disabling ETag generation can also simplify your caching strategy and reduce the number of requests to your server.

How to disable ETag generation in Next.js? 

To disable ETag generation in Next.js, you can set the generateEtags option to false in your custom server configuration. 

Creating Next.js Application:

Step 1: Install the latest version of Node.js and NPM on your machine if you haven’t already.

Step 2: Install the Next.js CLI globally by running the following command in your terminal:

npm install -g create-next-app

Step 3: Create a new Next.js project by running the following command in your terminal:

npx create-next-app my-app

Step 4: Once the project is created, navigate to the project directory and install the etag package by running the following command:

npm install etag

Project Structure: Project structure of Node.Js application:

Node.Js file structure

Example 1: Open the next.config.js file in the root of your project directory and add the following code:

Javascript

const etag = require('etag');

module.exports = {
    generateEtags: true,
    async headers() {
        return [
            {
                source: '/(.*)',
                headers: [
                    {
                        key: 'ETag',
                        value: etag(Date.now().toString()),
                    },
                ],
            },
        ];
    },
};

This code enables ETag generation for your Next.js project and sets the ETag header for every response with a unique ETag value.

Steps to run the application: Start your Next.js application by running the following command:

npm run dev

Output:

Verify that the ETag header is being set in the responses by opening your browser’s developer tools and checking the response headers for any requests. You’ve successfully created a Next.js application with ETag generation enabled.

In this example, the generateEtags option is set to false in the server configuration file, which disables ETag generation.

Note: Disabling ETag generation may not be suitable for all applications, and it’s important to understand the trade-offs involved. Without ETags, the server may have to send the entire page on every request, which can increase response times and put additional load on the server. If you’re using a caching layer, you may still want to generate ETags to improve cache efficiency.

Example 2: Here we are generating Etags for system Date Time and disabling the ETAG part as below. In this example, the Home component displays the current time and some data fetched from the server using getServerSideProps. The effect hook is used to update the time every second.

By default, Next.js generates an ETag for the response returned by getServerSideProps, based on the contents of the data prop. This ETag is included in the response headers sent to the browser, and the browser uses it to determine whether to use a cached version of the page or request a new version.

You can verify that the ETag is being generated by inspecting the response headers in your browser’s developer tools. Look for a header named ETag and you should see a value like “W/”5e5c04d0-5809”.

If you want to disable ETag generation, you can add the following code to your next.config.js file:

• index.js: Complete the running example and paste the same code into the index.js file.

Javascript

// pages/index.js

import { useEffect, useState } from 'react';

function Home({ data }) {
    const [time, setTime] = useState(Date.now());

    useEffect(() => {
        const interval = setInterval(() => {
            setTime(Date.now());
        }, 1000);
        return () => clearInterval(interval);
    }, []);

    return (
        <div>
            <h1>Hello, World!</h1>
            <p>The time is {new Date(time).toLocaleTimeString()}</p>
            <p>{data}</p>
        </div>
    );
}

export async function getServerSideProps() {
    const data = `Generated at ${new Date().toLocaleTimeString()}`;
    return {
        props: {
            data,
        },
    };
}

• Next.Config.Js: Next switch to the Next.Config.Js file and embed below Js code 

Javascript

// next.config.js

module.exports = {
    etag: false,
};

Output:

In summary, using ETags in Next.js can help improve the performance of your application by reducing the number of requests and amount of data transferred, while also ensuring that the client has the most up-to-date content available.