How To Create A Custom Image Loader In NextJS?

Last Updated : 07 Aug, 2024

Creating a custom image loader in Next.js allows you to control how images are loaded and optimized. This is useful for integrating with different image services or handling specific image processing needs. Here’s how to create and use a custom image loader: This article will walk you through the steps of creating a custom image loader in Next.js, from project setup to demonstration and output.

Approach

To create a custom image loader in Next.js, define a loader function to format image URLs. Pass this function to the loader prop of the <Image> component. Optionally, use environment variables for dynamic URL configurations.

Steps to Create Custom Image Loader in Next JS

Step 1: Setting Up a New Next.js Project

Initialize a next.js project in your preferred location by running the following command in the terminal.

npx create-next-app imgloaderdemo

Step 2: Navigate into the project directory

using following command navigate to project directory or simple open from vs code open folder option inside file available top left side.

cd imgloaderdemo

Step 3: Project Structure

We will create a custom loader component in the index.js file and we will use that custom loader to load our image.

The updated dependencies in package.json file:

"dependencies": {     "next": "14.2.3",     "react": "^18",     "react-dom": "^18", }

Step 4: Custom Image Loader Function

Next.js lets you define your own image loader function. This function accepts an object with parameters src, width, and quality and returns a URL string.
Make a new component for your customized loader. In the index file , and lets call it customLoader.
In the example, replace https://example.com/ with the base URL of your image hosting service. The loader constructs a URL that includes width and quality parameters.

Step 5: Integrate the Custom Loader

lets use this custom loader in our next.js application as following.
Here, we use the customLoader function and provide it to the Image component's loader prop. The src attribute should be relative to the base URL set in your loader function.

Step 6: Configuring next.config.mjs

If you are fetching images from an external source, make sure your Next.js configuration allows external images. Modify the next.config.mjs:
Replace 'firebasestorage.googleapis.com' with the domain of your image hosting service.

JavaScript

//src/pages/index.js import Image from "next/image";  const customLoader = ({     src,     width,     quality, }) => {     return `https://firebasestorage.googleapis.com     	/v0/b/shaikclone.appspot.com/o/     	${src}?alt=media&token=ca82acf3-426d-4cf1-872f-         5575eac7de55&w=${width}&q=${ quality || 75 }`; };  export default function Home() {     return (         <div style={{ height: "100vh" }}>             <h1>Custom Image Loader Demo</h1>             <Image                 loader={customLoader}                 src="gfglogo.jpg"                 alt="Sample Image"                 width={500}                 height={300}             />         </div>     ); }

JavaScript

// next.config.mjs  /** @type {import('next').NextConfig} */ const nextConfig = {     reactStrictMode: true,     images: {         domains: [             "firebasestorage.googleapis.com",         ],          //replace with your actual one for demonstration firebase is used.     }, };  export default nextConfig;

Step 7: Running the Application

Run your Next.js application to see the custom image loader in action:

npm run dev

Step 8: Testing the Custom Image Loader

Open your browser and go to http://localhost:3000. Your image should be loaded with the specified width and quality criteria set by your custom loader.

verifyloadedimg — verify this image should be loaded.

Step 9: Inspecting the Image URL

Inspect the image URL to ensure it matches the structure given in your own loader function.

HTML

<img     src= "https://firebasestorage.googleapis.com/v0/b/shaikc…n=ca82acf3-426d-4cf1-872f-5575eac7de55&w=640&q=75"     alt="Sample Image"     width="500"     height="300" />

The URL should include the width (w=500) and quality (q=75) parameters set in the customLoader function.

Note: The usage of Image in newest version of react throws an warning of fetchPrioriy, although it works fine. If you want to avoid error being logged The only solution found for this is to roll back in react version that is 18.2.0. hoping for a fix from react newer upcoming version.

Conclusion

Creating a custom image loader in Next.js enables you to interface with many image hosting services and tailor image loading behavior to your specific requirements. Using this approach, you can create a Next.js project, construct a custom image loader, and see it in action. This guarantees that your photos load efficiently and match your individual needs.

How to Load NextJS Images from an External URL ?

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