Page speed is one of the most important ranking factors in today’s search engine optimization.
For beginners, the fastest and simplest way to speed up the web page is to optimize large resources (like images), minimize the size, and thus reduce the load time.
In this blog post, I’d like to introduce the 10 best JavaScript libraries to lazy load large web content (like images, videos, iframes, etc) within the document that makes it possible to significantly increase page speed and enhance your page rankings.
I hope you like it and help me spread the world.
Originally Published Nov 28 2017, updated Jan 11 2023
Native Lazy Loading
For Chrome users, you can use the native lazy loading feature to lazy load web resources in the modern web app.
The new loading attribute which brings native <img> and <iframe> lazy-loading to the web:
<!-- Lazy-load an offscreen image when the user scrolls near it -->
<img src="unicorn.jpg" loading="lazy" alt=".."/>
<!-- Load an image right away instead of lazy-loading -->
<img src="unicorn.jpg" loading="eager" alt=".."/>
<!-- Browser decides whether or not to lazy-load the image -->
<img src="unicorn.jpg" loading="auto" alt=".."/>
<!-- Lazy-load images in <picture>. <img> is the one driving image
loading so <picture> and srcset fall off of that -->
<picture>
<source media="(min-width: 40em)" srcset="big.jpg 1x, big-hd.jpg 2x">
<source srcset="small.jpg 1x, small-hd.jpg 2x">
<img src="fallback.jpg" loading="lazy">
</picture>
<!-- Lazy-load an image that has srcset specified -->
<img src="small.jpg"
srcset="large.jpg 1024w, medium.jpg 640w, small.jpg 320w"
sizes="(min-width: 36em) 33.3vw, 100vw"
alt="A rad wolf" loading="lazy">
<!-- Lazy-load an offscreen iframe when the user scrolls near it -->
<iframe src="video-player.html" loading="lazy"></iframe>However, you may still need a third-party JavaScript library to implement the lazy load functionality on cross-browser projects.
The 10 Best Lazy Load JavaScript Libraries:
1. Responsive Image Lazy Load JS Library – lazysizes
lazysizes is an easy yet robust JS library used to delay the loading of images (iframes, scripts, etc) until they come into view, as well as loading the appropriate sources according to the breakpoints defined in the markup to fit any screen size.
2. Performant Element lazy Load Library – Lozad
A small (569 bytes minified & gzipped), highly performant JavaScript library used to lazy load Html elements (e.g. images, iframes, backgrounds, etc.) using Intersection Observer Web API.
3. Pure JavaScript Library For Lazy Loading Images – lazyload.js
lazyload.js is a stand-alone JavaScript library for lazy loading images without any dependencies. It supports the srcset attribute and with and takes best advantage from the progressive JPEG image format.
4. Lightweight Retina Ready JS Image Lazy Load Library – Layzr.js
A lightweight yet robust JavaScript library that delays the loading of images until they’re scrolled into view.
5. Easy Image Lazy Loading with blazy.js
A lightweight & easy-to-use script to delay the load of images until they enter the viewport. Helpful to save the bandwidth and reduce the server requests.
6. Modern Retina-ready Image Lazy Loader – lazyestload.js
A modern, fast, lightweight image lazy load JavaScript library that provides 2 methods to lazy load images with support for retina and responsive images.
7. Small Image/Video/Iframe Lazy Loader – yall.js
A really small JavaScript library to lazy load images, videos, iframe contents and background images as the users scroll through your content-heavy webpage.
8. Responsive Image Lazy Load JavaScript Library – responsivelyLazy
An ultra-light javascript library which allows you to delay the loading of appropriate images based on the width of their parent containers. Help you speed up the initial page load time to provide better user experience.
9. Pure JavaScript Native Lazy Loading Polyfill
A small vanilla JavaScript polyfill for the loading=”lazy” attribute.
10. Accessible Image Lazy Load In Pure JavaScript – gandul.js
A small accessible image lazy load library that works with the <a> link and supports responsive image delivery.
Conclusion:
This is a list of lazy load libraries implemented in vanilla JavaScript.
For jQuery users, don’t forget to check out our another list of 10 best lazy load plugins.