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1.2.0 • Public • Published

loading="lazy" attribute polyfill

MIT license loading-attribute-polyfill on Npmjs Total downloads ~ Npmjs jsDelivr CDN downloads Codacy Badge dependencies Status code style: prettier XO code style Conventional Commits Greenkeeper badge

Fast and lightweight vanilla JavaScript polyfill for native lazy loading, meaning the behaviour to load elements right before they enter the viewport. Provides graceful degradation, and is - not just thatfor - SEO friendly. Handles images with srcset and within picture, as well as iframe elements. loading="lazy" will be a huge improvement for todays web performance challenges, so use and polyfill it today!

  • Released under the MIT license
  • Made in Germany


  • Web standards: Supports the standard loading="lazy" attribute on image and iframe elements
  • Performance: It's based on highly efficient, best practice code.
  • SEO & crawlers: The image and iframe contents aren't being hidden from crawlers that aren't capable of scrolling.

Core concepts

The polyfill was designed with the following concepts kept in mind:

  • dependency-free
  • Using JavaScript with graceful degradation


Just integrate the JavaScript file into your code - et voilà.

You may optionally load via NPM or Bower:

$ npm install loading-attribute-polyfill
$ bower install loading-attribute-polyfill

You could even load the polyfill asynchronously:

Afterwards you'll need to wrap all of your <img> and <iframe> HTML tags that you'd like to lazy load (and thatfor added a loading="lazy" attribute as well) by an <noscript> HTML tag:

Simple image

<noscript class="loading-lazy">

Image wrapped in a picture tag

    <noscript class="loading-lazy">
            media="(min-width: 40em)"
                simpleimage.huge.jpg 1x,
                simpleimage.huge.2x.jpg 2x
                simpleimage.jpg 1x,
                simpleimage.2x.jpg 2x

Image with srcset

<noscript class="loading-lazy">
            simpleimage.1024.jpg 1024w,
            simpleimage.640.jpg   640w,
            simpleimage.320.jpg   320w
        sizes="(min-width: 36em) 33.3vw, 100vw"
        alt="A rad wolf"


<noscript class="loading-lazy">

Optional additional dependencies

In case you'd like to support older versions of Microsoft EDGE, Microsoft Internet Explorer 11 or Apple Safari up to 12.0, you could (conditionally) load an IntersectionObserver polyfill:

Nevertheless this polyfill would still work in those browsers without that other polyfill included, but this small amount of users wouldn't totally benefit from the lazy loading functionality - we've at least got you partly covered by using the Microsoft proprietary lazyloading resource hints.


Nothing really, just plug it in, it will should work out of the box.


See the polyfill in action either by downloading / forking this repo and have a look at demo/index.html, or at the hosted demo:

Further implementations - Kudos for that


Nico23 has developed a Wordpress plugin:

PHP Twig Extension

@tim-thaler has developed a PHP Twig Extension:

Craft Twig Loading Lazy plugin

@tim-thaler has developed a Craft Twig Loading Lazy plugin:


Credits for the initial kickstarter / script to @Sora2455 for better expressing my ideas & concepts and support by @diogoterremoto, @dracos and @Flimm. Thank you very much for that, highly appreciated !

Tested with

  • Mac

    • Mac OSX 10.14, Mozilla Firefox 68.0.1 (manually, localhost)
    • Mac OSX 10.14, Safari 12 (via CrossBrowserTesting)
    • Mac OSX 10.13, Safari 11 (via CrossBrowserTesting)
  • iOS

    • iPad 6th Generation Simulator, Mobile Safari 12.0 (via CrossBrowserTesting)
  • Windows

    • Windows 10, Google Chrome / versions latest & latest-1 (via CrossBrowserTesting)
    • Windows 10, Microsoft EDGE / versions 17, 18 (via CrossBrowserTesting)
    • Windows 10, Microsoft Internet Explorer / version 11 (via CrossBrowserTesting)

Big Thanks

Cross-browser testing platform provided by CrossBrowserTesting


things to keep in mind

  • The demo HTML code is meant to be simple

More information on the standard


If you're trying out and using my work, feel free to contact me and give me any feedback. I'm curious about how it's gonna be used.

And if you do like this polyfill, please consider even also having a look at the other polyfill we've developed:


npm i loading-attribute-polyfill

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