This proud CSS programmer is happy that we’ve finally got some merch going. We’re running teemill for now to gauge interest and we already have ideas for more stuff. piccalil.li/links/pic…

The vast majority of your users are not, in fact, using the latest and greatest iPhone. Lower-end Android devices far outweigh them, so it’s imperative to test on them and make them a part of your development workflow — especially if you use a JavaScript framework. csswizardry.com/2025/08/low-...

Returning after a social media hiatus and catching up on a lot of excellent #webperf posts. Thanks for sharing, everyone!

performance.now() is coming! The night before the conference, 29th of October, @mozilla.org organises performance.sync(), the pre-meetup where you can meet your peers to mentally prepare for two days of information overload. They're also looking for a few people to present. luma.com/ziykhh4y

Watching all the awesome folks in the #webperf community showing up to request Core Web Vitals in Safari:

Fam, I know a lot of you are still getting situated on bsky, but you gotta update your profile with a pic and a useful description ASAP. Folks over here (myself included) aggressively block anyone with a whiff of bot- or scam- like behavior.

I wrote a blog post that goes into detail on this: paulcalvano.com/2024-03-19-c... TLDR: if you are serving any dynamically generated responses on the server, then gzip level 6 or brotli 5 are reasonable defaults. If you -only- serve static cacheable resources then turn it up all the way.

I'll keep it short this year. We're so fortunate to have such an amazing gathering, where everyone is welcoming and welcomed no matter their experience level. My huge thanks as always to the #PerfNow organisers, speakers, and everyone who attended and made it a wonderful place to be. ♥️

performance.now() 2025 will take place on 30th and 31st of October, 2025. #perfnow.

It's a wrap! We made it! Take a minute to recover, let all those awesome new learnings percolate in your brain, and leave your notes and to-do lists for Monday. 🙂 #PerfNow

"Experimenting includes knowing whether the experiment worked." @anniesullie.bsky.social #PerfNow

Don't forget to celebrate success! 29,420 years of time saved across CWV in 2024! 🎉 @anniesullie.bsky.social #PerfNow

One last talk to go! #PerfNow

A very clear way to demonstrate the performance inequality gap. There's a direct correlation between Interaction to Next Paint (INP) scores and the amount of RAM on a user's device. @karlijnlowik.bsky.social @erwinhofman.bsky.social #PerfNow

I've recently been trying to optimise the layout shift that occurs when the fallback font swaps out for our branded web font. Super helpful to have this detailed walkthrough from @mandymichael.bsky.social! #PerfNow

Okay. Okay! I'll let you in on a secret. Last night I went to a karaoke bar with some lovely fellow #PerfNow attendees. Hopefully all video evidence has been expunged from the internet. We sang to Blink-182, Red Hot Chili Peppers, Backstreet Boys, and oh god I'm old

Day 2 of #PerfNow kicks off with @tkadlec.bsky.social telling us he's optimistic. "We have more options than ever in this community. I think we have more tools than ever. We're not going to solve performance by writing more bytes. Betting on the browser is our best chance at long-term success."

Thank the performance gods (and @debugbear.com!) for the wonderful barista! #PerfNow

Alas, it looks like Bluesky is still struggling to keep up with the new demand. 👋 #PerfNow from 2 hours ago!

A powerful talk from @slightlyoff.bsky.social at #PerfNow. 75% of new devices with browsers are phones. The web is not successful on mobile. Many things try to steal links from the web and move them to apps from closed, proprietary app stores. The web is losing.

It's simple, but easy to forget - "Your conditions are not the conditions of your user. Have empathy." But we all have moments where our conditions aren't ideal, so we all benefit from #webperf improvements. @szynszyliszys.bsky.social #PerfNow

Most web performance metrics and resources are developed with a privileged user in mind. At most, we suffer 'accidental' performance issues, like browsing on a train. For some, good web performance is not achievable at all. @szynszyliszys.bsky.social #PerfNow

All 17 performance mistakes: @paulcalvano.bsky.social #webperf #PerfNow

Me: *immediately messages a colleague* Yep. Guess I'll be tweaking our NGINX config next week. 😅 Thanks @paulcalvano.bsky.social! Love it when things get super practical at #PerfNow.

An example of a site with 379 unused preloads. I'm on the verge of tears. 😭 #PerfNow

No one goes to work to do a bad job. Clichéd perhaps, but it's important to treat mistakes without a blame culture. Create a learning opportunity. But that said, @paulcalvano.bsky.social is walking us through 17 #webperf mistakes that stem from best intentions but lead to worse results. #PerfNow

Web performance and accessibility go hand in hand. To make a radio button in Material UI, you need 6 HTML elements, 66 CSS selectors, and 30KB minified JavaScript. Don't throw out what the browser gives us for free. #PerfNow #webperf @ericwbailey.website

It's all for nothing if you don't have a plan for #webperf regressions. "Shall we pretend we haven't seen that?" isn't a plan! Having agreed rules based on the severity and duration of regressions to your KPIs means you don't need to ask permission to rollback. #PerfNow @csswizardry.com

Different members of teams and businesses need different levels of 'disclosure' on performance metrics. Your CEO probably doesn't need to know about TTFB! @csswizardry.com #PerfNow

A rather... sobering... start to the morning from @tammyeverts.bsky.social discussing the #webperf landscape. #PerfNow

We're starting #PerfNow off strong with a double bill of @tammyeverts.bsky.social and @csswizardry.com! Always great to hear from you both, and smart move to get your talks out the way so you can enjoy the rest of the conf!

Good moooooorning #PerfNow!

"Collecting UX-impacting metrics everyone understands means we can improve them together." Ideas from bsky.app/profile/kurt... for moving beyond Core Web Vitals to custom metrics relevant to your product that everyone can understand and get behind. #PerfNow #webperf

It's pre-conf conf time! #perfnow

My favourite thing about Amsterdam is wandering around, being on one side of a canal, and wondering how to get to the *other* side of the canal. Also, playing Frogger with bikes.

Hello Amsterdam! I'm so excited to be back for #perfnow, so stay tuned to hear me post excitedly about #webperf. First post-travel stop after a delayed train, Black Gold Coffee (slash record shop) to refuel. ☕

More accurately, I hadn't heard of #BTConf until lots of lovely folks started posting about it and sharing. It's definitely on my radar now. 🙂

I couldn't make it to #BTConf, thanks so much for sharing your slides + notes. I love hearing real-world experiences of this stuff. Pretty sure our main web app is doomed to forever have Minitest + RSpec tests, and we just started moving the JS tests from Mocha to Jest. And introducing Typescript. 😅

On the plus side, thanks everyone for the great user 'starter packs'. Now I'm in a lovely active #webperf / #webdev bubble. 🤗

Oh boy, I have to post here too?!