10 Best Lazy Loading JavaScript Libraries (2021 Update)

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 Feb 24 2021

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. Youtube LazyLoad

Youtube LazyLoad

Demo Download

Yet another Youtube lazy loader that delays the loading of Youtube video player to improve the performance of your web page.


2. Progressive Image lazy Loading With Blur Effect

Progressive Image lazy Loading With Blur Effect

Demo Download

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.


3. Responsive Image Lazy Load JS Library – lazysizes

Responsive Image Lazy Load JS Library - lazysizes

Demo Download

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. Designed for high performance websites to improve the page load time and to save the bandwidth.


4. Vimeo LazyLoad

Vimeo LazyLoad

Demo Download

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.


5. lazyframe.js

lazyframe.js

Demo Download

A native JavaScript library used to delay the loading of iframe content for Google Maps, Youtube/Vimeo/Vine videos and so on.


6. Pure JavaScript Library For Lazy Loading Images – lazyload.js

Pure JavaScript Library For Lazy Loading Images – lazyload.js

Demo Download

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.


7. Performant Element lazy Load Library – Lozad

Performant Element lazy Load Library Lozad

Demo Download

Lozad is a small (569 bytes minified & gzipped), highly performant JavaScript library used to lazy load any html elements (e.g. images, videos, etc.) using Intersection Observer Web API.


8. Small Image Lazy Loader – yall.js

Small Image Lazy Loader yall.js

Demo Download

yall.js is a really small JavaScript library to lazy load images as the users scroll through your content heavy webpage. Supports srcset attribute and picture element. Based on the Intersection Observer API.


9. LazyTube

LazyTube

Demo Download

An ultra-light Youtube video lazy load library which only loads/displays video thumbnails on the page and fetches the Youtube video player only when the thumbnail is clicked.


10. imagebuddy

imagebuddy

Demo Download

A pure JavaScript plugin for lazy loading images with support for custom placeholder and fallback.


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.

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