React

Real-time image resizing, automatic optimization, and file uploading in React using ImageKit.io.

This is a quick start guide to show you how to integrate ImageKit in a React application. The code samples covered here are hosted on Github: https://github.com/imagekit-samples/quickstart/tree/master/react.

This guide walks you through the following topics: ‌

Setup ImageKit React SDK

For this tutorial, it is recommended to create a dummy React app, as shown below.

Create a React app:

Let's use the create-react-app CLI utility provided by React to build a new project:

npx create-react-app imagekit-react-app

Navigate to the project directory:

cd imagekit-react-app/

Open up the project in your text editor of choice, and navigate to src/App.js. This is where we will do most of our work. It should look like this:

src/App.js
import React from 'react';
import logo from './logo.svg';
import './App.css';
function App() {
return (
<div className="App">
<header className="App-header">
<img src={logo} className="App-logo" alt="logo" />
<p>
Edit <code>src/App.js</code> and save to reload.
</p>
<a
className="App-link"
href="https://reactjs.org"
target="_blank"
rel="noopener noreferrer"
>
Learn React
</a>
</header>
</div>
);
}
export default App;

Now run the app:

npm start

In your web browser, navigate to http://localhost:3000/

You should see the dummy app created by React CLI. Now we can begin our work.

Install the ImageKit React SDK:

Installing the ImageKit React SDK in our app is pretty simple:

npm install --save imagekitio-react

Initialize the React SDK:

Before the SDK can be used, let's learn about and obtain the requisite initialization parameters:

  • urlEndpoint is a required parameter. This can be obtained from the URL-endpoint section or the developer section on your ImageKit dashboard.

  • publicKey and authenticationEndpoint parameters are optional and only needed if you want to use the SDK for client-side file upload. These can be obtained from the Developer section on your ImageKit dashboard.

// required parameter to fetch images
const urlEndpoint = '<YOUR_IMAGEKIT_URL_ENDPOINT>';
// optional parameters (needed for client-side upload)
const publicKey = '<YOUR_IMAGEKIT_PUBLIC_KEY>';
const authenticationEndpoint = 'https://www.your-server.com/auth';

Note: Do not include your API private key in any client-side code, including this SDK or its initialization. If you pass the privateKey parameter while initializing this SDK, it will throw an error.

ImageKit Components:

This SDK provides 3 components:

You can import components individually:

import { IKImage, IKContext, IKUpload } from 'imagekitio-react';

Configure the app for ImageKit:

Let's remove the existing dummy code in src/App.js file, then add the urlEndpoint:

src/App.js
import React from 'react';
import './App.css';
const urlEndpoint = '<YOUR_IMAGEKIT_URL_ENDPOINT>';
function App() {
return (
<div className="App">
</div>
);
}
export default App;

Rendering images

Loading image from relative path:

Remember the default image we mentioned earlier? It should be available at the following URL:

https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/default-image.jpg

Let's fetch and display it! For this, we will use the IKImage component.

Import IKImage from the SDK:

import { IKImage } from 'imagekitio-react';

Now let's add it to our App. Along with the image path prop, it also needs the prop for urlEndpoint:

<IKImage
urlEndpoint={urlEndpoint}
path="default-image.jpg"
/>

Rendered HTML element:

<img src="https://ik.imagekit.io/demo/default-image.jpg?ik-sdk-version=react-1.x.x" alt="">

The App.js file should look like this now:

src/App.js
import React from 'react';
import './App.css';
import { IKImage } from 'imagekitio-react';
const urlEndpoint = '<YOUR_IMAGEKIT_URL_ENDPOINT>';
function App() {
return (
<div className="App">
<h1>ImageKit React quick start</h1>
<IKImage
urlEndpoint={urlEndpoint}
path="default-image.jpg"
/>
</div>
);
}
export default App;

Your React app should now display the default image in its full size:

Full sized image (1000px x 1000 px)

You can pass styles and other attributes as props. For e.g. lets add 400px width by adding the width prop:

<IKImage
urlEndpoint={urlEndpoint}
path="default-image.jpg"
width="400"
/>

This is how the output should look now:

Resized image (width=400px)

Note that here we have set the width to 400px at the <img> tag level only. Intrinsically, the fetched image is still 1000px wide.

Loading image from an absolute path:

If you have an absolute image path coming from the backend API e.g. https://www.custom-domain.com/default-image.jpg then you can use src prop to load the image.

For example:

<IKImage
urlEndpoint={urlEndpoint}
src="https://ik.imagekit.io/demo/default-image.jpg"
width="400"
/>

The output looks like this:

Render image on custom domain via absolute path

Setting ImageKit context for the SDK

It is not necessary to specify the urlEndpoint in every instance of IKImage. This can be managed much more easily with the IKContext component.

IKContext is a wrapper that can be configured with your SDK initialization parameters. Pass your urlEndpoint to it as a prop, and you're good to go!

Let's go ahead and import it within the App.js file:

import { IKContext, IKImage } from 'imagekitio-react';

Now add the IKContext component to the render function:

<IKContext urlEndpoint={urlEndpoint}></IKContext>

Let's nest our IKImage components within it, so that those can access the urlEndpoint from the context wrapper.

src/App.js
import React from 'react';
import './App.css';
import { IKContext, IKImage } from 'imagekitio-react';
const urlEndpoint = '<YOUR_IMAGEKIT_URL_ENDPOINT>';
function App() {
return (
<div className="App">
<IKContext urlEndpoint={urlEndpoint}>
<h1>ImageKit React quick start</h1>
<IKImage path="default-image.jpg" width="400" />
<h2>Loading image from an absolute path</h2>
<IKImage
src="https://ik.imagekit.io/demo/default-image.jpg"
width="400"
/>
</IKContext>
</div>
);
}
export default App;

Basic image manipulation

Let’s now learn how to manipulate images using transformations.

The React SDK gives a name to each transformation parameter, e.g. height for h and width for w parameter. It makes your code more readable. If the property does not match any of the available options, it is added as it is. See the full list of supported transformations in React SDK on Github.

You can also use h and w parameter instead of height and width. See the complete list of transformations supported in ImageKit here.

Height and width manipulation

‌To resize an image along with its height or width, we need to pass the transformation object as a prop to IKImage.

Let’s resize the default image to 200px height and width:

<IKImage
path="default-image.jpg"
transformation={[{
height: 200,
width: 200
}]}
/>

Rendered HTML element:

<img src="https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/tr:h-200,w-200/default-image.jpg?ik-sdk-version=react-1.x.x"
path="default-image.jpg"
alt="">

Refresh your browser to get the resized image.

Resized Image (200x200px)

Quality manipulation

You can use the quality parameter to change image quality like this:

<IKImage
path="default-image.jpg"
transformation={[{ quality: 10 }]}
width="400"
/>

Rendered HTML:

<img src="https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/tr:q-10/default-image.jpg?ik-sdk-version=react-1.x.x"
path="default-image.jpg" width="400" alt="">
Quality manipulation (q=10)

Crop mode

Let’s now see how cropping works. We will try the extract crop strategy. In this strategy, instead of resizing the whole image, we extract out a region of the requested dimension from the original image. You can read more about this here.

<IKImage
path="default-image.jpg"
transformation={[{
height: 300,
width: 200,
cropMode: 'extract',
}]}
/>

Rendered HTML element:

<img src="https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/tr:h-300,w-200,cm-extract/default-image.jpg"
path="default-image.jpg"
alt="">
Crop Mode Extract (200x300px)

Chained transformation

Chained transformations provide a simple way to control the sequence in which transformations are applied.

Let’s try it out by resizing an image, then rotating it:

<IKImage
path="default-image.jpg"
transformation={[{
height: 300,
width: 200
}]}
/>

Transformation URL:

<img src="https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/tr:h-300,w-200/default-image.jpg"
path="default-image.jpg"
alt="">
Resized and cropped (200x300px)

Now, rotate the image by 90 degrees.

<IKImage
path="default-image.jpg"
transformation={[{
height: 300,
width: 200,
}, {
rt: 90,
}]}
/>

Chained Transformation URL:

<img src="https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/tr:h-300,w-200:rt-90/default-image.jpg"
path="default-image.jpg"
alt="">
Resized, then rotated

Let’s flip the order of transformation and see what happens.

<IKImage
path="default-image.jpg"
transformation={[{
rt: 90,
}, {
height: 300,
width: 200,
}]}
/>

Chained Transformation URL:

<img src="https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/tr:rt-90:h-300,w-200/default-image.jpg"
path="default-image.jpg"
alt="">
Rotated, then resized

Adding overlays to images

ImageKit.io allows you to add text and image overlay dynamically.

For example, a text overlay can be used to superimpose text on an image. Try it like so:

<IKImage
path="default-image.jpg"
transformation={[{
height: 300,
width: 300,
overlayText: 'ImageKit',
overlayTextFontSize: 50,
overlayTextColor: '0651D5',
}]}
/>

Rendered HTML element:

<img src="https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/tr:h-300,w-300,ot-ImageKit,ots-50,otc-0651D5/default-image.jpg"
path="default-image.jpg"
alt="">
Text Overlay (300x300px)

Lazy-loading images in React

You can lazy load images using the loading prop in IKImage component. When you use loading="lazy", all images that are immediately viewable without scrolling load normally. Those that are far below the device viewport are only fetched when the user scrolls near them.

The SDK uses a fixed threshold based on the effective connection type to ensure that images are loaded early enough so that they have finished loading once the user scrolls near to them.

You should always set the height and width of the image element to avoid layout shift when lazy-loading images.

<IKImage
path="default-image.jpg"
transformation={[{ height: 300, width: 400 }]}
loading="lazy"
height="300"
width="400"
/>

Rendered HTML element:

<img src="https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/tr:h-300,w-400/default-image.jpg?ik-sdk-version=react-1.x.x"
path="default-image.jpg" loading="lazy" height="300" width="400" alt="">

Blurred image placeholder

To improve user experience, you can use a low-quality blurred variant of the original image as a placeholder while the original image is being loaded in the background. Once the loading of the original image is finished, the placeholder is replaced with the original image.

// Loading a blurred low quality image placeholder
// while the original image is being loaded
<IKImage
path="default-image.jpg"
lqip={{ active: true, quality: 20 }}
width="400"
/>

Combining lazy loading with low-quality placeholders

You have the option to lazy-load the original image only when the user scrolls near them. Until then, only a low-quality placeholder is loaded. This saves a lot of network bandwidth if the user never scrolls further down.

// Loading a blurred low quality image placeholder
// and lazy-loading original when user scrolls near them
<IKImage
path="default-image.jpg"
transformation={[{ height:300, width:400 }]}
lqip={{ active:true }}
loading="lazy"
height="300"
width="400"
/>

Uploading files in React

Let's now learn how to upload an image to our media library.

React SDK provides IKUpload component which renders an input type="file" tag that you can use to upload files to the ImageKit media library directly from the client-side.

To implement this functionality, a backend server is needed to authenticate the request using your API private key.

Setup the backend app

For this quickstart guide, we will create a sample Node.js server which will provide an authentication endpoint at http://localhost:3001/auth.

Let's create a file index.js inside server folder in the project root.

mkdir server
touch server/index.js

Install the basic packages needed to create a dummy server for ImageKit backend authentication:

npm install --save express imagekit

We will use the ImageKit Node.js SDK to implement http://localhost:3001/auth.

The backend SDK requires your API public key, private key, and URL endpoint. You can obtain them from Developer Options and URL-endpoint pages respectively.

This is how server/index.js file should look now. Replace <YOUR_IMAGEKIT_URL_ENDPOINT>, <YOUR_IMAGEKIT_PUBLIC_KEY> and <YOUR_IMAGEKIT_PRIVATE_KEY> with actual values:

Node.js
Node.js
server/index.js
/*
This is our backend server.
Replace YOUR_IMAGEKIT_URL_ENDPOINT, YOUR_IMAGEKIT_PUBLIC_KEY,
and YOUR_IMAGEKIT_PRIVATE_KEY with actual values
*/
const express = require('express');
const app = express();
const ImageKit = require('imagekit');
const imagekit = new ImageKit({
urlEndpoint: '<YOUR_IMAGEKIT_URL_ENDPOINT>',
publicKey: '<YOUR_IMAGEKIT_PUBLIC_KEY>',
privateKey: '<YOUR_IMAGEKIT_PRIVATE_KEY>'
});
// allow cross-origin requests
app.use(function(req, res, next) {
res.header("Access-Control-Allow-Origin", "*");
res.header("Access-Control-Allow-Headers",
"Origin, X-Requested-With, Content-Type, Accept");
next();
});
app.get('/auth', function (req, res) {
var result = imagekit.getAuthenticationParameters();
res.send(result);
});
app.listen(3001, function () {
console.log('Live at Port 3001');
});

authenticationEndpoint should be implemented in your backend. The SDK makes an HTTP GET request to this endpoint and expects a JSON response with three fields i.e. signature, token, and expire. Learn how to implement authenticationEndpoint on your server.

Let's run the backend server.

cd server
node index.js

You should see a log saying that the app is “Live on port 3001”.

If you GET http://localhost:3001/auth, you should see a JSON response like this. Actual values will vary.

{
token: "5dd0e211-8d67-452e-9acd-954c0bd53a1f",
expire: 1601047259,
signature: "dcb8e72e2b6e98186ec56c62c9e62886f40eaa96"
}

Configure authentication in the frontend app

Now that we have our authentication server up and running, let's configure the publicKey and authenticationEndpoint in the frontend React app:

Add the following to src/App.js file to initialize the SDK with auth params:

const publicKey = '<YOUR_IMAGEKIT_PUBLIC_KEY>';
const authenticationEndpoint = 'http://localhost:3001/auth';

Now, pass these values as props into a new IKContext instance which will hold our upload component:

<IKContext publicKey={publicKey} urlEndpoint={urlEndpoint} authenticationEndpoint={authenticationEndpoint} >
{/* ...child components */}
</IKContext>

This is how src/App.js should look now. Replace <YOUR_IMAGEKIT_URL_ENDPOINT> and <YOUR_IMAGEKIT_PUBLIC_KEY> with actual values:

src/App.js
import React from 'react';
import './App.css';
import { IKContext, IKImage } from 'imagekitio-react';
const urlEndpoint = '<YOUR_IMAGEKIT_URL_ENDPOINT>';
const publicKey = '<YOUR_IMAGEKIT_PUBLIC_KEY>';
const authenticationEndpoint = 'http://localhost:3001/auth';
function App() {
return (
<div className="App">
<IKContext
urlEndpoint={urlEndpoint}
publicKey={publicKey}
authenticationEndpoint={authenticationEndpoint}
>
{/* ...client side upload component goes here */}
</IKContext>
{/* ...other SDK components added previously */}
</div>
);
}
export default App;

Upload an image

For this, we will use the IKUpload component. Let's import it from the SDK into our App.js file:

import { IKContext, IKImage, IKUpload } from 'imagekitio-react';

Add the IKUpload component nested within IKContext, as well as a couple of event handlers for upload error and success, onError and onSuccess respectively:

React JSX
React JSX
src/App.js
import React from 'react';
import './App.css';
import { IKContext, IKImage, IKUpload } from 'imagekitio-react';
const publicKey = '<YOUR_IMAGEKIT_PUBLIC_KEY>';
const urlEndpoint = '<YOUR_IMAGEKIT_URL_ENDPOINT>';
const authenticationEndpoint = 'http://localhost:3001/auth';
const onError = err => {
console.log("Error", err);
};
const onSuccess = res => {
console.log("Success", res);
};
function App() {
return (
<div className="App">
<h1>ImageKit React quick start</h1>
<IKContext
publicKey={publicKey}
urlEndpoint={urlEndpoint}
authenticationEndpoint={authenticationEndpoint}
>
<p>Upload an image</p>
<IKUpload
fileName="test-upload.png"
onError={onError}
onSuccess={onSuccess}
/>
</IKContext>
{/* ...other SDK components added previously */}
</div>
);
}
export default App;

This is how it looks in the UI:

Upload Image

Direct file uploading from the browser

Let’s now upload an image by selecting a file from the file input.

When you choose a file, the file is immediately uploaded. You can pass optional onSuccess and onError callback functions as props like we have.

You can verify that file was successfully uploaded by checking the browser console. In case of success, it should print a success message, like this:

Upload Success Response

The response object would look similar to this (values may vary):

{
fileId: "5f7d39aa80da9a54b1d7976a",
filePath: "/test-upload_0GfSgMm4p.png",
fileType: "image",
height: 298,
name: "test-upload_0GfSgMm4p.png",
size: 5748,
thumbnailUrl: "https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/tr:n-media_library_thumbnail/test-upload_0GfSgMm4p.png",
url: "https://ik.imagekit.io/<YOUR_IMAGEKIT_ID>/test-upload_0GfSgMm4p.png",
width: 298,
}

After a successful upload, you should see the newly uploaded image in the Media Library section of your ImageKit dashboard.

If you don't see the image, check if there are any errors in the browser console log. Then verify whether the API private key has been configured correctly in the server app and if the server app is running.

Fetching uploaded file

Fetch uploaded image and show in UI using IKImage with the filePath returned in the upload response.

<IKImage path="/test-upload_0GfSgMm4p.png" />

The app should display your uploaded image correctly!

Error boundaries

We strongly recommend using Error Boundaries to handle errors in the React UI. ErrorBoundary is used to gracefully handle errors anywhere in the child component tree of a React app.

It can be used to log errors and display a fallback UI instead of the component tree that crashed.

Example:

<ErrorBoundary>
<IKImage publicKey={publicKey} urlEndpoint={urlEndpoint} path={path}
transformation={[{
height: 300,
width: 400
}]}
/>
</ErrorBoundary>

What's next

The possibilities for image manipulation and optimization with ImageKit are endless. Learn more about it here: