🎤 I’m speaking at #LeedsJS TONIGHT! Free to attend. Be there or be aspect-ratio: 1; www.meetup.com/leeds-js/eve...

🩺 Meet Your Users Where They Are with Obs.js csswizardry.com/2026/05/meet...

An important update courtesy of @tunetheweb.com! csswizardry.com/2026/05/bett...

Show, don’t tell! A couple of years ago, I ran a custom INP workshop for a client, and built an interactive demo to show them what their site FEELS like. Today, I decided to polish it and publish it!

I’ve been working with a client who runs a lot of social media and ad campaigns, so we’ve been deploying the experimental `No-Vary-Search HTTP` header. It’s amazing to see it actually working! Read all about it here: csswizardry.com/2026/05/bett...

‼️ BEWARE! `font-family` Doesn’t Fall Back the Way You Think: csswizardry.com/2026/04/font...

Play with it here: jsbin.com/toriwawari/e...

PSA, this is why you keep seeing Times New Roman all over your site. #CSS #CLS #Typography

🎨 I gotta say, my latest is a little treasure trove: what even is `contain`?! csswizardry.com/2026/04/what...

I miss #WebDayOut :(

reading: What Is CSS Containment and How Can I Use It? csswizardry.com/2026/04/what... — my prayers were answered! Harry explains all 🙏 for my next wish...

100% agree with this! Browsers are AMAZING at loading a page in mostly the right way by default. There are lots of extra options (fetchpriority, loading=lazy) to tweak that further if you know with reasonably certainly that they could benefit from those. If it’s ambiguous, then leave it be.

🚫 When All You Can Do Is All or Nothing, Do Nothing For all you weekend warriors, advice for times of uncertainty. csswizardry.com/2026/03/when...

🇳🇱 Freshly back from a wonderful working week in The Hague. I shall never tire of this beautiful city.

Well, Brighton, you’ve been stunning as always. Thank you so much to @adactio.com and the @clearleft.com team for having me at #WebDayOut, an invigorating and inspiring shot in the arm to kick conference season off proper.

Me looking at standardised web APIs like… #WebDayOut

Hello and good morning from Brighton, where I attend #WebDayOut. If you want to follow along visually, here is my set of photos that document the day. More to follow. marcthiele.com/photos/web-d...

Slides from my #WebDayOut talk, ‘Build for the Web, Build on the Web, Build With the Web’. Incredibly proud of this one. speakerdeck.com/csswizardry/...

And we’re off! #WebDayOut

Hey, Bluesky! Have some blue sky. I’m in beautiful Brighton for @clearleft.com’s #WebDayOut tomorrow. Who else is here?

I’ve been consulting for 12 years and I still get a real rush every time an enquiry comes in. An amazing feeling!

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 /**//*//**/