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

Incredible Demos

  • By
    MooTools Link Fading

    We all know that we can set a different link color (among other properties) on the hover event, but why not show a little bit more dynamism by making the original color fade to the next? Using MooTools 1.2, you can achieve that effect. The MooTools...

  • By
    Build a Calendar Using PHP, XHTML, and CSS

    One of the website features my customers love to provider their web users is an online dynamic calendar. An online calendar can be used for events, upcoming product specials, memos, and anything else you can think of. I've taken some time to completely...

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!