React 19.2 has shipped including support for the DevTools Extensibility API so you can understand what React is doing when, and how that relates to the rest of the performance profile 🥳 🎉 react.dev/blog/2025/10...

When your colleague isn't looking, update their ChatGPT personalisation setting to only action things when they say "Simon says". 🤫

MCP Server fever! Following on from the robots.txt MCP server release of yesterday, today I've launched one for you web perf fans! Query the CrUX API in your favorite AI tool Example: youtu.be/et7Og7_Ii6E?... Get the details here: tamethebots.com/tools/cwv-hi... #WebPerf #CWV #CoreWebVitals

Core Web Vitals mystery for ya: Why does Google Search Console same my LCP is bad, but every example URL has good LCP? I see developers asking: How can this happen? Is GSC wrong? (I'm willing to bet it is not!) What can you do about it? This is admittedly confusing so let's dive in... 🧵 1/12

Added a MCP Server for @not-a-robot.com and my robots.txt testing tool. Get the details here: tamethebots.com/tools/robots...

SvelteKit has support for deploying to Cloudflare, Netlify, and dozens of other platforms www.sveltesociety.dev/packages?cat...

here's how i implement lazy loading in Astro (and it's transferable to any SSG) lukealexdavis.co.uk/morsels/mors...

⚠️Security PSA: ⚠️ If anyone used Cancelo[dot]io SaaS - make sure you have removed their flow.js from your website. The domain expired, and someone has replaced the js with malware 👹

SVGOMG has been updated to use SVGO 4! (thanks Adrien Crivelli!) This is the URL for SVGOMG. Unfortunately someone maintains a fork with ads, so, err, don't use that 😀 jakearchibald.github.io/svgomg/

This is cool and been waiting for No-Vary-Search to escape Speculation Rules (where this was originally started) to the more general use case. This allows you to say that certain client-side URL params (e.g. gclid or other analytic params) can be ignored and still use the resource from the cache.

This was truly excellent, and you can still go catch up on YouTube (with plenty of other talks) and it's never too late to send donations!

#Showerthoughts: Who was the first person to start all the "5-door car" shite? Like a car that has the standard 4 doors + a boot ("trunk" for my US friends). THAT'S NOT FIVE DOORS. A BOOT IS NOT A DOOR. I bet it was a marketer.

Nice. MCP server for devtools. developer.chrome.com/blog/chrome-...

I wrote this. I am happy to have written it. searchengineland.com/hidden-promp...

Authentication for your personal crawlers & SEO tools is going to be more and more of a topic. This is a simple guide to get started (though I imagine it'll evolve significantly over time).

shameless plug: lukealexdavis.co.uk/posts/dont-o...

Today I Learn, there is such thing as a JavaFish. I wonder if it too is worried about copyright clams from Oracle? en.wikipedia.org/wiki/Java_barb

ELSc (Electric Light Solo Cellist)

I think I broke ChatGPT. It's now saying cats.txt is an actual thing for SEO. 🤣 It's funny people say to use this for SEO. Note: This is an incognito, logged out ChatGPT conversation, so this isn't due to personalisation or memory.

i wrote about how templating your reports is cool as long as you don't stay rigid with them

REQUEST: Anybody have a pretty active WordPress blog and a relatively quiet Bluesky account that wants to help me test a WordPress plugin this afternoon? May need you to know where your logs are :) - and sit on a short call. DM's are open or you can drop an email to dwinrhys.com/contact-me/

2025: 0 of the Global Top 200 Websites Use Valid HTML: With the latest results from the annual HTML conformance analysis, the legend of what may be the most difficult language in the world continues to grow.

Color lovers, I've got a new tool for you to convert, generate and explore OKLCH colors: oklch.fyi/ I like being able to tweak a whole color ramp, adapting chroma to make it more or less vibrant.

Bye Bye CrUX Dashboard, I'll always be nostalgic for your stacked bars of Goodness: developer.chrome.com/blog/crux-da... You can use tamethebots.com/tools/cwv-hi..., the cruxvis.withgoogle.com or one of the many other great free tools that use the CrUX History API.

Developers adding AI features to your favourite shopping list app.

Search Console's binning some of the filters for some depreciated search appearances. Find out more here (including advice if you're exporting to BigQuery and relying on queries involving these) developers.google.com/search/blog/...

my masterpiece

You can prompt inject Gemini/API/Vertex by engineering images that contain hidden messages when downscaled. Maybe has potential for blackhat SEO, giving AI agent instructions on what to like/not like, what to do. Try asking Gemini what text is in this image: i83.uk/core.png

Good job! We’re almost ready to switch these over to be the default and turn off the old audits as explained here: developer.chrome.com/blog/moving-... Have you switched over to the new Insights yet?

3 easy steps to unfuck GA4 if you're a marketer. Step 1. Tell your client they need an AI channel in GA4. Step 2. Read the tutorial, set a source for your channel with a regex Step 3. Select the custom channel group to show it in the main GA4 report.

Hey folks, I'm looking to schedule the next PerformanceObserver meetup and need some new CFP submissions. I have a few experienced #webperf speakers on there, but I like to break it up with either newer speakers or new-to-webperf speakers. performanceobserver.dev/call-for-pap...

The GoFundMe for Alan is now live at www.gofundme.com/f/alan-bleiw...

Errrm, hashtag what?

📊 Here’s the 2025 State of Learning in SEO 72% of SEOs learn from industry news sites. 16% say events are a waste of time. SEJ, BrightonSEO and SEOFOMO come out on top. Read the full study ➡️ www.lidia-infante.com/post/state-o...

Show us your best tooling ideas to help developers adopt more modern web features! Join the hackathon for your shot at $10,000 in cash prizes 🔥🔥 web.dev/blog/baselin...

Great post and it's been a pleasure helping @krzksz.bsky.social and @yoav.ws get this working on Shopify. performance.shopify.com/blogs/blog/s...

🩺 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/

Another one following the rule that every app eventually becomes a messaging app www.theverge.com/news/765771/...

Some notes on the insecurity baked into Perplexity's Comet "AI Browser" - the Brave security team reported serious prompt injection vulnerabilities in it, but Brave themselves are developing a similar feature that looks doomed to have similar problems simonwillison.net/2025/Aug/25/...

Pretty sure we all have relatives or friends who aren't tech savvy and you worry about getting scammed online. Well now you can invite a robot version of them to live in your browser, with access to you credit card and login details How could that ever go wrong! guard.io/labs/scamlex...

New in Chrome DevTools: Instantly check CSS feature compatibility with Baseline! Chrome DevTools now displays the Baseline status for CSS properties right in the Elements panel - Baseline gives you clear info about which web features are ready to use today.

Well there you have it... It's SerpAPI. Note, Perplexity is also a customer of theirs -> Sources: OpenAI has been partially using Google search results scraped by a startup called SerpApi for ChatGPT responses on current events like news and sports

Another brilliant episode of search of the record from @divingfor.fun & @johnmu.com, who energetically discuss lazy loading. Also made my day to hear a brief mention of my name (but don't let that put you off 😉) youtu.be/XgkhNF1gDKA?...

New @httparchive.org analysis about sites adding AI Bots and Crawlers to their robots.txt files. While robots.txt doesn't "block" bots by itself, it's a clear demonstration of the preferences of site owners and the sentiment towards AI crawlers on today's web. paulcalvano.com/2025-08-21-a...

My cat when it's time for flea drops

Slightly diminish an historical website: GeoVillages

"How is it possible for CrUX to say 90% of page loads are good, and Google Search Console to say only 50% of URLs are good. Which is right?" It's a question I get about Core Web Vitals and I admit it's confusing, but the truth is both are correct because they are different measures... 1/5 🧵

Two pro webperf tips! Are you using Annotations in your performance traces? developer.chrome.com/docs/devtool... And even when not needing to annotate, Gemini AI auto-annotations can quickly give you an idea what a bit of the flame chart is doing without you needing to dig in yourself. Try it out!

LLM hallucinations will cause real-world harm and deaths. Been saying this for a while, like @lilyray.nyc ⤵️ I note the small irony that hallucinations caused hallucinations. www.nbcnews.com/tech/tech-ne...