Build for the Web, Build on the Web, Build with the Web csswizardry.com/2025/01/buil...

(Anyone traveling Schiphol to Centraal please be advised that Sprinter trains are anything but.)

🇬🇧 ✈️ 🇳🇱 To @perfnow.nl! My favourite week of the year.

You know you should be testing your site or app with low and mid-tier mobiles, but what exactly does that *mean* for 2025? What's low-end? What's mid-tier? What are people using right now? @csswizardry.com gets into which phones would work well, what emulations to use, and why it's important.

What a beautiful trip to Toronto for @fitc.ca. Thank you so much for having me.

Not only is @jpamental.bsky.social a really good friend, he’s an exceptionally good MC. You should hire him for your event.

If your company has just laid you off, sneak `v` and `version` into the allowlist before you leave 👀

Allowlisted params (e.g. ?utm_source) can be reused in HTTP cache!

[email protected] showed me this hyper elegant deep-link approach that @cloudflare.social provide: `dash dot cloudflare dot com/?to=/:account/:zone/speed/optimization/protocol` This lets you select your Cloudflare account and zone before taking you to its correct Protocol dashboard!

I recently started instrumenting both @cloudflare.social and browser cache hits/misses and the numbers, while obvious, are compelling. The best request is the one that never happens. Check that 0ms TTFB 😍 ℅ @speedcurve.com

Build for the web, Build on the web, Build with the web. An excellent take from @csswizardry.com on progressive enhancement, SPA frameworks and staying as close to the platform as possible. csswizardry.com/2025/01/buil...

🔮 I held three of my 1:1s in the last 24hr and it’s amazing to see (and shape) what folk are working on. Different project, different audiences, different scales, but all so fun to help out with.

I would wholeheartedly recommend this by the way. 2:1 salt:MSG used anywhere you’d use salt in a savoury context. Amazing on meat and green vegetables.

Huge news from @cloudflare.social! blog.cloudflare.com/the-rum-diar...

What a privilege to be speaking at one of @adactio.com’s events! It’s only taken about 15 years…

performance.now() is coming! As tooling improves, is performance testing becoming any easier? @csswizardry.com, who spends every day auditing client projects,, thinks confusion has increased. Let's ensure that every test we run has a purpose and gives us useful data. perfnow.nl/speakers.htm...

Friends and fans of Obs.js, please consider lending your vote for Interop 2026: github.com/web-platform...

I’ve spent a bit of the weekend doing some analysis of my newsletter and it’s blown me away. I’ve definitely been neglecting it. Over 4,000 of you with >55% open rate and >15% click rate. That’s way way WAY above the industry average. You folk are incredible! So supportive ❤️

🪄 If you’ve ever wondered where the name CSS Wizardry came from (and why on earth it stuck), I’m telling newsletter subscribers the full back story later today: csswizardry.com/newsletter/

This is one of the best talks I’ve ever seen. Give it 20 minutes of your weekend.

And if this interests you, I wrote about it OVER A DECADE ago: 24ways.org/2013/keeping...

I think a lot of folk tend to forget that @github.com Gists are Git repositories like any other, just lacking most of the GUI functionality. This means they’re a great place to store long-lived, version-controlled, distributed, shareable documents.

Please stop inheriting the box-model. The supposed use-case for that is extremely out-dated, inheritance doesn't really help, and it actively makes real box-sizing use-cases more difficult! This #CSS best practice was never the best to begin with: www.oddbird.net/2025/09/04/b...

🤝 If you were thinking about subscribing but think your boss should pay for it, there is a corporate tier: csswizardry.gumroad.com/l/subscribe?...

I just optimised a single interaction by 5× from 350ms down to to 70. This is an interesting one as it was caused by something designed to *improve* performance. I made a six-minute screencast showing how I found and fixed it. 👉 Subscribers already know how: csswizardry.gumroad.com/l/subscribe

💡 I did the research so you don’t have to! This is every element in current Baseline browsers that would need a margin or padding removing in a reset stylesheet: gist.github.com/csswizardry/...

🩺 You don’t *have* to use Obs.js to adapt your site. You can use it as an analytics add-on and send data off to @speedcurve.com! csswizardry.com/Obs.js/demo/...

I wanted to create a slightly tighter lockup for Obs.js’ logo and `h1` but I didn’t want the two to ever touch. Solution? A little dead-zone (coloured red) attached to `::after` which occupies the area overing the j’s descender.

Binary code paths with /**//*//**/

Worth adding that git ships with a helper called diff-highlight that you can use with a few tweaks to gitconfig: github.com/git/git/tree...

Commit this character sequence to memory: /**//*//**/

`--word-diff` and `--word-diff-regex` are your new favourite Git tips:

🪄 Really neat trick for docs/demo pages. You can add `display: block` to `script` and `style` and show folk the actual, literal code you’re running. It’s what I do with Obs.js:

1. Have a device lab that runs Baseline browsers. 2. Get ChatGPT to build you a page with one of every non-deprecated HTML element. 3. Write a little script that `getComputedStyle` of everything. 4. Compile and dedupe the list for each browser. 5. Merge the lists. 6. Should have just used * {}

💡 I did the research so you don’t have to! This is every element in current Baseline browsers that would need a margin or padding removing in a reset stylesheet: gist.github.com/csswizardry/...

🩺 Obs.js is now OPEN SOURCE! I’d love early feedback and I’ll showcase any of your implementations on the demo page: csswizardry.com/Obs.js/demo/

As a developer, I’ve always struggled with design. I know/appreciate what looks nice, but I can never get there myself. Anyway, I spent a few hours this morning working on a small logotype for Obs.js. Based on Gotham, I’m pretty happy with the results so far.

Did you know there’s work going on to add a `random()` function to CSS?? You can try it out today in Safari Technology Preview. Learn what it means, how to use it and see a bunch of examples at: webkit.org/blog/17285/r...

Toying around with some silly things on my Friday evening.

👀 I’ve been working on a little something! There’s a link to the demo in the video description. www.youtube.com/watch?v=IMww...

Chrome DevTools snippets are incredibly powerful, but they don’t accept parameters. One crude way around it is to use `prompt()` to take input on the fly.

I added a section about making better device choices on @catchpointsystems.bsky.social’s #WebPageTest: csswizardry.com/2025/08/low-...

Really really really good web perf article :3

Chrome DevTools snippets are incredibly powerful, but they don’t accept parameters. One crude way around it is to use `prompt()` to take input on the fly.

Simulate a randomly busy main thread (i.e. Input Delay) with this snippet: (()=>{const r=(a,b)=>a+(Math.random()*(b-a)|0); setInterval(()=>setTimeout(s=>{for(let d=Date.now(); Date.now()-d<=s;); console.log('Blocked '+s+'ms')}, r(0,100), r(0,100)), r(500,2500))})();

One key thing I want people to take away from this: ‘low-tier’ doesn’t necessarily mean ‘old’.

🤳 Over the weekend, I did some research. What are good, representative, real-world devices for performance testing in 2025? csswizardry.com/2025/08/low-...

🦋 It took far longer than I’d like to admit, but I made @bsky.app a desktop-installable app. If anyone wants the snippet, get at me.

🦋 It took far longer than I’d like to admit, but I made @bsky.app a desktop-installable app. If anyone wants the snippet, get at me.

It finally happened!