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When I think about web performance, the first thing that comes to my mind is how images are generally the last elements that appear on a page. Today, images can be a major issue when it comes to performance, which is unfortunate since the speed a website loads has a direct impact on users successfully doing what they came to the page to do (think conversation rates).

Very recently, Rahul Nanwani wrote up an extensive guide on lazy loading images… Read article

You might not know this, but JavaScript has stealthily accumulated quite a number of observers in recent times, and Intersection Observer is a part of that arsenal. Observers are objects that spot something in real-time — like birdwatchers going to their favorite place to sit and wait for the birds to come.

Different observers observe different things (not everyone watches hawks).

The very first observer I came to know was the Mutation Observer that looks for changes to the DOM … Read article

There have been several excellent articles exploring how to use this API, including choices from authors such as Phil Hawksworth, Preethi, and Mateusz Rybczonek, just to name a few. But I’m aiming to do something a bit different here. I had an opportunity earlier in the year to present the VueJS transition component to the Dallas VueJS Meetup of which my first article on CSS-Tricks was based on. During the question-and-answer session of that presentation I was … Read article

There are a few different "traditional" ways of lazy loading of images. They all require JavaScript needing to figure out if an image is currently visible within the browser's viewport or not. Traditional approaches might be:

• Listening to scroll and resize events on the window
• Using a timer like setInterval

Both of these have performance problems.… Read article

Images are critical. Whether it is marketing banners, product images or logos, it is impossible to imagine a website without images. Sadly though, images are often heavy files making them the single biggest contributor to the page bloat. According the HTTP Archive’s State of Images report, the median page size on desktops is 1511 KB and images account for nearly 45% (650 KB) of that total.

That said, it’s not like we can simply do away with images. They’re … Read article

You may have heard (or even issued the call) that “we can just use lazy loading!” when looking for a way to slim down a particularly heavy web page.

Lazy loading is a popular technique for gradually requesting images as they come into view, rather than all at once after the HTML of the page has been parsed. It can reduce the initial page weight, and help us hit our performance budgets by requesting images when they're needed.

It can … Read article

A "slider", as in, a bunch of boxes set in a row that you can navigate between. You know what a slider is. There are loads of features you may want in a slider. Just as one example, you might want the slider to be swiped or scrolled. Or, you might not want that, and to have the slider only respond to click or tappable buttons that navigate to slides. Or you might want both. Or you might want to … Read article

We're in the future now so, of course, we're working on ways to speed up the web with fancy new tactics above and beyond the typical make-pages-slimmer-and-cached-like-crazy techniques.

One tactic, from years ago, was InstantClick:

Before visitors click on a link, they hover over that link. Between these two events, 200 ms to 300 ms usually pass by (test yourself here). InstantClick makes use of that time to preload the page, so that the page is already there when

Some fantastic behind-the-scenes stuff about Stripe's design work by Benjamin De Cock. Absolutely everything is clever and using very modern techniques.

• Using CSS grid for their iconic background stripes
• Using 3D cubes for aesthetic flair
• Using reduced motion media queries to accommodate that preference
• Using the Web Animation API for event-triggered keyframe-like animations in JavaScript

Plus one I'd never seen before:

Connect's landing page uses the new Intersection Observer API which provides a much more robust and performant way to

As a UI designer, I’m constantly reminded of the value of knowing how to code. I pride myself on thinking of the developers on my team while designing user interfaces. But sometimes, I step on a technical landmine.

A few years ago, as the design director of wsj.com, I was helping to re-design the Wall Street Journal’s podcast directory. One of the designers on the project was working on the podcast player, and I came upon Megaphone’s embedded player.… Read article