PerfReviews

We Improve Your Website's Performance Increase your revenue and make your users happier with our web auditing and optimization services 👉 perf.reviews/en #WebPerf #Performance #PerfReviews

With 2 years of rollouts, we've learned a lot about compression dictionaries and the Web. Patrick will cover what works, where the footguns are, how to maximize their effectiveness, and other experiments around compressing content on the web. @patmeenan.com at perfnow.nl

During last week's @nywebperf.com Meet4Speed session, we analyzed the performance of an eCommerce website and found a very peculiar font bug that resulted in 3 formats of the same font being loaded. paulcalvano.com/2026-10-18-i...

🎉 WebPerformance Report Week #42 is out! ✅ Join our growing community: ⚡ Performance Report 🛡️ Security Report ♿ Accessibility Report 📊 Analytic Report 🔎 SEO Report Explore our report catalog 👉 webperformancereport.com#Catalog #webperf #websecurity #a11y #analytics #seo #ai

WebPerf Snippets started as a collection of snippets to paste into the DevTools console. With version 2.0, they are also built for AI agents to run webperf-snippets.net 🧵 #WebPerf #AI

During a perf audit for a client, I read this in a PR: "The module should only be loaded once, not every time a file is selected." When I read it, something didn't add up, so I started digging. And the result surprised me. I wrote a post joanleon.dev/en/dynamic-i... #JS #WebPerf

Thank you so much @veneman.dev 🥰 Two awesome new stickers on my laptop from a great project: @projectwallace.com #CSS #CSSTools #WebPerfTools

How far ahead browsers fetch lazy images: • Chrome: 1,250px on 4G, 2,500px on 3G, 6,000px (!!) on 2G • Firefox: 600px, on any connection • Safari: one viewport. Lazy iframes: 0px, they wait until on screen

So happy to share mine & @nicj.net's first @cloudflare.social blog post—during our 16th Birthday Week no less! 🥳 Today we announce BEACON, a #webperf research dataset we're contributing to the @rumarchive.com community. blog.cloudflare.com/how-fast-is-...

The case against JPEG XL Investigating JPEG XL's place as a Web image codec, by @giannirosato.com, via @webperfreport.bsky.social giannirosato.com/blog/post/ca... #JPEGXL #JXL #ImagePerf #WebPerf

P75 is green: LCP 1.58s, INP 176ms, CLS 0.01. P90: LCP 2.68s, INP 352ms, CLS 0.17. 15% of visits get a noticeably worse experience. Product Performance doesn't end once you pass CrUX: if P75 is good, work on P90. #WebPerf #CoreWebVitals #RUM #ProductPerformance

🤩 Fantastic article by @nucliweb.net on HTTP cache partitioning and the #CrossOriginStorage API: joanleon.dev/en/http-cach.... Try the embedded demos with the COS extension installed or in one of the experimental browser builds (see the Awesome Cross-Origin Storage list: github.com/tomayac/awes...).

Five reports. Five dimensions. One place. ✨ We’re just a few days away from launching our new Google Search Console Report. With SEO, our 360° reporting vision now covers: ⚡ Performance 🔐 Security ♿ Accessibility 📊 Analytics 🔎 SEO Coming soon. 🚀 #webperf #SEO #UX

If you use @speedcurve.com—and you should—then LUX Sidecar is for you! csswizardry.com/2026/08/intr...

“The performance issues erode trust. Users rarely report performance problems directly; they simply leave, convert less often, or switch to competitors.” - @denodell.bsky.social www.manning.com/books/fast-b... #WebPerf #FastByDefault #PerfEngineering

In my audits, the question I hear most after a deploy is "why hasn't CrUX moved yet?" The window is always 28 days; daily, weekly and monthly are just cadences over the same data. And p75 resists change by design I explain it with two interactive demos joanleon.dev/en/crux-28-d... #WebPerf #CrUX

Most skills are a Markdown file that grows out of control and gets loaded whole, even when the task doesn't need it. Modern Web Guidance inverts the pattern: 250 fixed tokens, and the agent retrieves the guide it needs on demand. joanleon.dev/en/modern-we... #AI #WebDev #CodingAgents

Reading a Performance Timeline by @nucliweb.net. This would be great for people who still have issues with Performance Timeline in Chrome. I love the form of this site. perf.reviews/profile-guide

This is an excellent explanation of the lag that exists in CrUX data Recently had a customer who made huge improvements to INP but it took nearly four weeks for it to show in CrUX

In my audits, reading the Performance profile is where people get stuck: the flame chart and waterfall look like noise at first I built an interactive guide to make them click, every figure is interactive, plus LCP, CLS, INP and the Insights panel perf.reviews/profile-guide #WebPerf #DevTools

An occupational habit: I open DevTools on every site I visit, hunting for things to improve. On skills.addy.ie I caught a 301 on every internal click, a wasted round trip. It was a trailing-slash mismatch. Wrote up the finding and the fix: joanleon.dev/en/trailing-... #WebPerf #Astro #Netlify

“Most teams fall into a reactive performance decay cycle: ship, wait for complaints, panic, patch, repeat. The Fast by Default model provides a repeatable alternative that keeps systems healthy.” Performance Engineering in Practice, by @denodell.bsky.social #WebPerf #Performance

Llevo tiempo viendo demos de multiagentes y casi todas sufren de lo mismo: un agente escribe y otro revisa... para acabar haciendo una todo-app No son malas demos, pero no hay un motivo técnico real para dividirlas en agentes. Así no aprendemos cuándo sí tiene sentido Hilo con una alternativa 👇

Safari and Firefox change how big sites render based on the domain. TikTok, Netflix, Instagram… even SeatGuru. Chrome doesn’t. Why is that? denodell.com/blog/browser... by @denodell.bsky.social #Browser

¿Buscas optimizar el rendimiento de tus aplicaciones con agentes de IA? En este workshop aprenderás a conectar el Chrome DevTools MCP a un agente para automatizar la detección de problemas. Veremos cómo generar reportes técnicos, de cliente y de management 👇 ¡Inscríbete aquí! #WebPerf #AI #MCP

Running performance audits by hand, scripts in DevTools, results scattered, is fine until you're doing it on every project I built PerfReviews Insights to skip that. URL in, structured report out. Fonts, images, CSS, LCP, TTFB. Pro accounts keep full history perf.reviews/insights #WebPerf

El agente de IA no sabe debuggear rendimiento si tú no le das el contexto para hacerlo. No es que sea malo. Por defecto trabaja a ciegas: sin acceso al navegador, sin trazas reales. #WebPerf #Performance #AIAgents #ChromeDevTools #Frontend

WebPerf Snippets meets AI agents: Orchestration without hallucination slides.com/joanleon/web... #WebPerf #WebPerfSnippets #PerfTools

Join us tomorrow for two great talks from Alfonso Moure and @nucliweb.net ! #webperf All details at... performanceobserver.dev

I've finished the #WebGPU in the browser series. 4 articles: fundamentals, image processing, real-time ML, and video editing Never written a shader before starting. In the last article we process video at 2ms per frame with WebGPU + WebCodecs joanleon.dev/en/webgpu-br... #WebPerf #JavaScript

Toggle CSS classes in bulk, then reset the scroll: two lines that force the browser to block the main thread synchronously. I documented how to detect it in the Performance Panel and why one requestAnimationFrame is not enough to fix it. #WebPerf #CSS #DevTools #JavaScript

The DebugBear custom dashboards feature is live now! We provide a flexible interface where you can display the web performance data that matters to your team. youtu.be/96fFkixiC8Y

Thanks to Codemotion for giving me the opportunity to continue sharing my knowledge on #WebPerf (aka improving the UX), and to do so in a workshop format where we use Chrome DevTools MCP to identify performance issues on a website with AI agents. #WebPerf #PerfTools #DevTools #CodemotionMadrid

A Gaussian blur in Canvas 2D takes 280ms. The same filter with WebGPU: 8ms. I wrote the second article in the WebGPU series: image processing in the browser with WGSL shaders and real benchmarks. joanleon.dev/en/webgpu-im... #WebPerf #WebGPU #JavaScript #Performance

I wrote about the experimental chrome-devtools-mcp CLI: a persistent daemon and direct subcommands to control Chrome from the terminal without writing code. Network, performance, Lighthouse, memory, interactions. All from the shell. joanleon.dev/en/chrome-de... #WebPerf #DevTools #JavaScript

Just published the first article of a series. Covers what WebGPU is, CPU vs GPU for performance, and when to use it (vs WebAssembly). Next: image processing, ML inference, and real-time video, with real code and benchmarks. 👉 joanleon.dev/en/webgpu-br... #WebPerformance #WebGPU #JavaScript

Sometimes opportunities come along that push you out of your comfort zone. An international product, millions of visits, and impact at scale. Definitely an exciting challenge. #WebPerf #CoreWebVitals #PerfChallenge

Software is evolving fast. My focus hasn’t changed: helping teams improve performance, UX, and conversion AI generates working code faster than ever… but not optimized for performance That’s where we add value: from “it works” to “it’s excellent” Reading @addyosmani.bsky.social’s new book

WebPerformance Report is no longer just a weekly report in your inbox Well done, @webperfreport.bsky.social team #WebPerf #Accessibility #Performance #Security #WebPerfReport

A measurement that varies with the model's interpretation is not a measurement. It's an estimate. I've written about separating deterministic measurement from AI analysis in web performance audits. #WebPerf #Performance #PerfReview #AI #DevTools

IA en auditorías de Web Performance: medición determinística e informes accionables perf.reviews/blog/ai-web-... #WebPerf #Performance #PerfReviews #PerfAudit #AI

React SSR Framework Showdown: TanStack Start, React Router, and Next.js Under Load blog.platformatic.dev/react-ssr-fr... by @nodeland.dev #React #Performance

Muchas webs siguen sirviendo imágenes PNG de 2–3 MB. Pero esas mismas imágenes pueden pesar menos de 50 kB. La optimización de imágenes sigue siendo uno de los mayores problemas de rendimiento en la web. Hilo 👇

Chrome is bringing AI directly into the browser with the Summarizer API. In this post I show how to add an AI-generated summary to blog posts using the Chrome Summarizer API and models running locally in the browser. No external APIs. No token costs. #AI #WebAI #JavaScript #Chrome

Anyone been experimenting with this? The team are looking for feedback so we can decide on next steps. Would love to hear feedback (good or bad!) on this issue: github.com/WICG/nav-spe...