Lazy Load IFRAMEs

By  on  

We've known for a decade that lazy loading resources like JavaScript, CSS, and especially images is a massive performance win for web pages. At first we used tricks and JavaScript to do the lazy loading, but more recently native image lazy loading has debuted in browsers.

Did you know that you can also lazy load IFRAMEs using the same loading="lazy" attribute and value?

<iframe 
    src="https://davidwalsh.name/"
    loading="lazy"
    onload="alert('Loaded!');"
/>

You can see how lazy loading IFRAMEs works with this demo:

See the Pen IFRAME Lazy Load by David Walsh (@darkwing) on CodePen.

This single attribute to perform a complex but useful operation is the ideal solution for lazy loading just about anything. I'm so thankful that browsers are implementing APIs that make using best practices so easy!

Recent Features

  • By
    Tips for Starting with Bitcoin and Cryptocurrencies

    One of the most rewarding experiences of my life, both financially and logically, has been buying and managing cryptocurrencies like Bitcoin, Litecoin, Ethereum. Like learning any other new tech, I made rookie mistakes along the way, but learned some best practices along the way. Check out...

  • By
    CSS 3D Folding Animation

    Google Plus provides loads of inspiration for front-end developers, especially when it comes to the CSS and JavaScript wonders they create. Last year I duplicated their incredible PhotoStack effect with both MooTools and pure CSS; this time I'm going to duplicate...

Incredible Demos

  • By
    Create a CSS Flipping Animation

    CSS animations are a lot of fun; the beauty of them is that through many simple properties, you can create anything from an elegant fade in to a WTF-Pixar-would-be-proud effect. One CSS effect somewhere in between is the CSS flip effect, whereby there's...

  • By
    Introducing MooTools NextPrev

    One thing I love doing is duplicating OS functionalities. One of the things your OS allows you to do easily is move from one item to another. Most of the time you're simply trying to get to the next or the previous item.

Discussion

  1. This browser feature looks really like a huge gamechanger. Would love so much to use it with profit although it doesn’t seem to work correctly for me.

    [First of all, using it with images instead of iframes always worked perfectly, so all this regards only loading=”lazy” for iframes.]

    After hours of testing on different pages, what I see is that using loading=”lazy”, Iframes load WAY TOO EARLY.

    This apparently buggy behavior happens only if the page itself is NOT loaded from another iframe. So this rules out CodePen as a viable tool to show this.

    Let’s make a text.html file from this code, almost identical to your example, to highlight exactly what I’m saying:
    https://gist.github.com/jeff-at-livecanvas/bb1a803465419c62d623305daf6722cd

    Opening this file in a Chrome window, with an internal height of 700 pixels, shows the Loaded! message immediately.
    Same happens with latest Firefox too.

    Would be great if somebody could shed some light on this.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!