Lazy Load IFRAMEs
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:
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!
![fetch API]()
One of the worst kept secrets about AJAX on the web is that the underlying API for it, XMLHttpRequest, wasn't really made for what we've been using it for. We've done well to create elegant APIs around XHR but we know we can do better. Our effort to...
![Creating Scrolling Parallax Effects with CSS]()
Introduction
For quite a long time now websites with the so called "parallax" effect have been really popular.
In case you have not heard of this effect, it basically includes different layers of images that are moving in different directions or with different speed. This leads to a...
![CSS :target]()
One interesting CSS pseudo selector is :target. The target pseudo selector provides styling capabilities for an element whose ID matches the window location's hash. Let's have a quick look at how the CSS target pseudo selector works!
The HTML
Assume there are any number of HTML elements with...
![Image Reflections with CSS]()
Image reflection is a great way to subtly spice up an image. The first method of creating these reflections was baking them right into the images themselves. Within the past few years, we've introduced JavaScript strategies and CANVAS alternatives to achieve image reflections without...
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.