Tim Kadlec

My talk from last year's @perfnow.nl is now out. Come for the dad jokes & advice on how to troll your kids, stay for my thoughts on stubborn empathy for our users as the foundation for web perf & two threats to the web: the monoculture and the machine. www.youtube.com/watch?v=Dvpi...

Six early-bird tickets left. Will they run out today? Or are you feeling lucky and wait for Monday? perfnow.nl/tickets.html

Ticket sales are open! perfnow.nl/tickets.html

📝 New post: Losing Focus timkadlec.com/remembers/20... Expressing some concerns I have about how all the AI-buzz is causing our industry to lose focus on what matters: the actual human beings using what we build.

I wrote "Your Voice" in 2016 to encourage people new to speaking & writing to be yourself, to find what's authentic for you and make sure you let that shine through in what you create. Seeing so many social posts and blog posts clearly written by AI—it feels more important today than 10 years ago.

I'm very excited about this! Have seen some really significant impact in our tests. With the sizes of websites and JS payloads continuing to increase, this is both important and impactful.

Really excited to see the support for compression dictionaries that @cloudflare.social is working on. Great background on the feature as well.

p75 and p90 JavaScript bytes on the web have exploded since May, 2025—easily the largest 10 month period based on HTTP Archive data since 2023. The long-tail is getting worse, very quickly. Gemini, what happened in May 2025?

Doing my part to keep customer support people employed and paid one annoying and frustrated "please let me talk to a real person and never make me use this useless AI support again" message at a time.

Wow this is very, very good! @whitep4nth3r.com

The somewhat ironic part about all the backlog of code to review thanks to AI coding tools is that AI is _significantly_ better at code review than it is at code generation.

Live view of me waiting for this day... Gonna be a lot of fun with some awesome stuff to come!

Do I know anyone, or does anyone I know know anyone, at eBay who I can chat with about some things I'm running into with their API's?

AI automated support bots are one of the worst plagues to infest the internet. They are truly awful, infuriating and useless 95% of the time. Please, I am begging, just let me talk to a real person.

AI will have to pry em dashes out of my cold dead hands Interesting conversation I had with my kids recently: my high-school daughters actively avoid using "big" words in their writing because they get accused of using ChatGPT. Literally dumbing down their writing to avoid being accused of using AI

I do firmly believe that if you're an individual or company that is NOT over-indexing on AI right now, you have the competitive advantage. Unfortunately I do not have high hopes that the industry will recognize that until significant damage has been done.

Very happy to work on a tool like that with @tkadlec.bsky.social and the team! Please try it out and post the issues and PRs.

At the airport heading back after another incredible #perfnow. Each year, I'm reminded of how fortunate I am to be a part of the performance community. So many wonderful, kind, smart people all working together to make the web better. Already looking forward to next year.

performance.now() 2026 will take place on 19th and 20th of November 2026. #perfnow.

Always, always happy to see @yoav.ws get a shout-out. So much incredible work has happened because of him. Most recent example—speculation rules in WebKit. #perfnow

Telescope, the new cross-browser performance testing agent I mentioned at #perfnow that we @cloudflare.social have open-sourced is here: github.com/cloudflare/t... We want this to be a tool the entire community is able to contribute to and benefit from, so please help us make it better!

I appreciate everyone at #perfnow letting me have my "old man yells at cloud" moment this morning. Slides are now up: noti.st/tkadlec/3imH...

I have been sooooo looking forward to this! SPA heuristics are gonna be such a huge step forward for measuring perf on the web and finally having hard data on the perf impact. @mmocny.com #perfnow

Fellow #perfnow fellows, a reminder that PerfPlanet calendar is coming this December for another edition. And it needs YOU. Please ask if you have any contribution ideas or concerns calendar.perfplanet.com/contribute/

“We should treat accessibility as something that is structural or baked in or part of the DNA, if we want to be successful” — says @marcysutton.com at #perfnow “Don’t treat it like trying to put chocolate chips into a cookie after it is baked” I love this framing!

@inesakrap.bsky.social starting her #perfnow talk with Lego's and Bluey has me already a fan.

Slides from my @perfnow.nl talk — How Fast Is Fast Enough? — are up! If you’re at #PerfNow (or even if you’re not) I’d love to talk about creating a delightful experience for your users. speakerdeck.com/tammyeverts/...

Friendly reminder! #perfnow

@tammyeverts.com opening #perfnow with How fast is fast enough? #pragmagical

It is Friday, end of week. A good time to grab your ticket for #btconf Berlin. 3 weeks to go and we still have seats available. Full list of #speakers, their #talks and #schedule here on our website. beyondtellerrand.com/events/berli...

Ridiculously clever from @scottjehl.com

This is super exciting, particularly knowing Safari has it in Tech Preview so we're _this_ close to having it cross-browser. Also fun to watch the rollout through the lens of Cloudflare's Web Analytics.

If your industry would die if you did the right thing perhaps it's not a good industry?

New case study on wpostats.com Relive improved LCP by 50% and cut out layout shifts and saw a 3% increase in conversion rate, 6% decrease in bounce rate and 9% increase in page views per session. wpostats.com/2025/10/02/r...

Been a hot minute, but working through some of the case studies that were submitted to wpostats.com but not yet put live. Starting with a pair of INP-relevant studies from PubTech and ContentSquare. wpostats.com/2025/09/15/p... & wpostats.com/2025/09/15/c...

👀 Safari plans to ship LCP and INP in 2025?! Be still my beating heart. webkit.org/blog/16458/a...

This is incredible data from @dbelson.com showing HTML requests from crawlers versus referrals from that platform. Very easy to see the cost of AI here. ClaudeBot: 70.9k requests : 1 referral (!!!) OpenAI: 1.6K : 1 Perplexity: 202.4 : 1 blog.cloudflare.com/ai-search-cr...

Pumped for this. The line-up is stacked (with more coming soon) & the community around the event has gotten better and better each year with amazing conversations throughout, side events, large standards & browser involvement—it's wild to think about how this has taken off from its 1st year.

Lake Superior remains undefeated

For those of you who watched my talk at @webexpo.bsky.social, the bug I mentioned regarding speculation rules and GET/POST looks like it should be fixed in Chrome v138. chromium-review.googlesource.com/c/chromium/s... h/t @tunetheweb.com

Thanks again to everyone who came to my #WebExpo talk about the intersection of site speed, #UX and business metrics – and how to make a data-driven business case for investing in #webperf. My slides are up. I'd love to hear your questions and feedback! speakerdeck.com/tammyeverts/...

Heading home after a great #webexpo with a nice mix of old friends and new. Doesn't hurt that Prague is beautiful with ample dessert options. :)

I’m speaking at @perfnow.nl this October about Accessibility and Performance! Super looking forward to it. perfnow.nl/speakers.html

In all my years of flying, my luggage has been lost three times and three times only. I have been to Prague three times and three times only. The venn diagram is a full circle.

I'm just a guy, sitting in front of his computer, begging companies to please stop making me talk to AI "support" and let me talk to an actual human being instead.

Been wondering why a bunch of sites have been SUPER slow lately. Turns out it's the @1password.bsky.social chrome extension doing really bad things. :/ Gonna have to disable for awhile.

One thing about deadlifts: if you get sloppy with your form, you'll be _painfully_ aware of it. This message has been brought to you by lower back pain.

Drinking plenty of mulled wine and watching Rudolph, as our forefathers intended.

This is so well deserved. Not only is Pat one of the most brilliant people I've ever had the opportunity to work with, but he's so generous with his time—I wouldn't be able to do what I do without all the times over the years that Pat patiently answered my questions and helped me figure things out.