srcattribute of the image
Lazy loading is technique that defers loading of non-critical resources at page load time. These non-critical resources are loaded at the moment of need.
When we lazy load images and video, we reduce initial page load time, initial page weight, and system resource usage, all of which have positive impacts on performance.
jQuery Smartify loads images, calls Ajax, plays with css classes in on demand, while element is/or becoming visible in device Viewport. It's replacement of jQuery Lazyload.
JAIL is a jQuery plugin that lazy load images making your page load faster. Images are downloaded when they are visible or when they become visible inside the viewport
Layzr.js is a small, fast, modern, and dependency-free library for lazy loading images.
jQuery.loadScroll is a simple jQuery plugin for dynamically loading images while scrolling.
Tada is a lightweight, no dependency library for lazy image load. jQuery plugin is also provided. Duplicate element check, throttled scroll handler, percent threshold supported.
bLazy is a lightweight lazy loading image script. It lets you lazy load and multi-serve your images so you can save bandwidth and server requests. The user will have faster load times and save data loaded if he/she doesn't browse the whole page.
lazysizes is a fast lazyloader for images (including responsive images), iframes and scripts/widgets without any dependency. It may become also your number one tool to integrate responsive images.
BttrLazyLoading is a jQuery plugin that allows your web application to defer image loading until images are scrolled to but not only! BttrLazyLoading also allows you to have different version of an image for 4 differents screen sizes: phones (<768px), tablets (≥768px), desktops (≥992px) and large Desktops (≥1200px).
Lazyload Any is a jQuery plugin provides a lazyload function for images, videos, iframe or anything.
Lazy Load XT is a mobile-oriented, fast and extensible jQuery plugin for lazy loading of images/videos with build-in support of jQueryMobile framework.
Echo.js is a simple image lazy loading library, it's less than 1KB minified.
Lazy-loading works by only loading the assets needed when the elements 'would' be in view, which it'll get from the server for you upon request, which is automated by simply changing the image src attribute.