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 23 2025
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. Display Blurry Placeholders While Loading Images – unlazy
An SEO-friendly and framework-agnostic lazy loading library that displays a blurry image placeholder until the original image is completely loaded.
2. 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.
3. Lazy Load Embed YouTube Player – youtube-iframe
A JavaScript library that easily adds Lazy Loading functionality to your Youtube videos embedded in your document.
4. Progressive Image lazy Loading With Blur Effect
A small script to progressively load images with a blur effect. The script will show your low res image with a progressive blur until the high res image has been loaded entirely.
5. 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.
6. Lazy Load iFrame Embedded Content With JavaScript – lazyframe.js
A native JavaScript library used to delay the loading of iframe content for Google Maps and Youtube/Vimeo/Vine videos.
7. Lazy Load Vimeo Video Player Until You Click The Thumbnail – Vimeo LazyLoad
Vimeo LazyLoad is the sibling project of the Youtube LazyLoad that load Vimeo video player on-demand when the user clicks on the play button & thumbnail image.
8. Delay The Loading Of Anything With Defer.js
A small and lightweight JavaScript library that delays the loading of web resources to improve page speed.
9. Load Youtube Video Only When Needed – Youtube LazyLoad
Yet another Youtube lazy loader that delays the loading of Youtube video player to improve the performance of your web page.
10. 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.
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.