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

Testing PerfReviews Insights #WebPerf #Performance #PerfReviews #CoreWebVitals

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

🚀 PerfReviews Insights: two new metrics to audit your web performance We've added two new analyses to the tool: #WebPerf #Performance #PerfReviews #WebPerfInsights

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...

I built a free tool to analyze web performance: no login, no setup. Paste a URL → get an instant report on images, videos, page weight and third-party scripts. It's in beta. Try it 👇 #WebPerf #Performance #PerfInsights

Starting with Chrome 145, DevTools now lets you throttle specific requests instead of the whole page. It’s the ideal way to test how your app handles a single slow asset or API call → goo.gle/4aP1Tcc

Today I’d like to thank Leboncoin for the opportunity to collaborate with their team over the past few weeks. It was a pleasure to analyze their platform, work on improving observability, and share methodologies to identify and prioritize Web Performance optimization opportunities.

WebPerf Snippets agent-first WebPerf Snippets SKILLs were written for humans: emojis, colours, tables. The agent had to parse all of that. I added structured JSON returns and a build with terser that removes the console code. 80 lines → ~300 characters. #WebPerf #AI #Performance

Practical guide to the <img> element: from basics to LCP. @nucliweb.net shows how srcset, sizes, modern formats AVIF and WebP via <picture>, fetchpriority, preload for the LCP image, and CDNs can improve Core Web Vitals. #performance #html joanleon.dev/en/guia-prac...

The JPEG XL Image Coding System History, Features, Coding Tools, Design Rationale, and Future arxiv.org/pdf/2506.05987 #Image #JpegXL

I've been using WebPerf Snippets in my audits for years. Scripts to measure LCP, INP, CLS, TTFB, Render Blocking... The next step: turning them into tools an AI agent can use autonomously. But there's a design decision that makes all the difference. 🧵 #WebPerf #WebPerformance #AI #DevTools #MCP

I've encountered many applications with poor INP due to long tasks that do not yield control to the browser I've written a guide with measurable examples comparing setTimeout, queueMicrotask, scheduler.postTask. It includes snippets to audit your projects joanleon.dev/en/yield-to-... #WebPerf

Last week I delivered a Web Performance training for part of the Basetis technical team: 2 days of theory and hands-on practice with real cases. We covered Core Web Vitals, RUM & Lab monitoring, Chrome DevTools, Lighthouse CI, Playwright and more... at the iconic La Pedrera. #WebPerf #Training

Interested in the @httparchive.org and not sure where to start? During the @performanceobserver.dev meetup tomorrow (12:30pm ET), I'm going to be providing an overview of the HTTP Archive and demonstrate how to start querying it! performanceobserver.dev/events/episo...

Optimize rendering with content-visibility joanleon.dev/en/content-v... #WebPerf #Performance #CSS

I've been updating WebPerf Snippets for Chrome DevTools, and this weekend brought 10 new tools for diagnosing web performance directly from the console. New snippets in webperf-snippets: 🧵 #WebPerf #WebPerformance #ChromeDevTools #CoreWebVitals #JavaScript #WebDev

🚀 New WebPerf Snippet published! Detects preload resource hints for scripts that use async or defer attributes. This is an anti-pattern that wastes bandwidth & can hurt performance by artificially elevating the priority of resources that should load at lower priority #WebPerf #WebPerfSnippet

🚀 New WebPerf Snippet published! Detects potential performance issues with `rel="prefetch"` resource hints by analyzing quantity, size, type, and appropriateness of prefetched resources. webperf-snippets.nucliweb.net/Loading/Pref... #WebPerf #WebPerfSnippet #PerfTools

Here's your friendly reminder that CSS selectors are global and evaluated RTL, so if you have selectors that are very broad like `.container > div` you might be impacting performance in a measurable way 🙈 Before and after profile of server switching after some selector optimizations in @discord.com

@nolanlawson.com’s talk from PerfNow a few years back is well worth a watch — covers some of the selector performance issues along with the optimisations browsers have introduced nolanlawson.com/2023/01/17/m...

Excited to share my latest contribution to the Web Performance Calendar 2025! In this post, I dive into using Chrome DevTools for debugging web performance, with tips to help you speed up your sites and improve user experience. #WebPerf #Performance #DevTools #PerfTools

Debugging web performance with Chrome DevTools. @nucliweb.net shows how to triage big assets in Network, read CrUX live Core Web Vitals, and use Performance Insights and traces to improve LCP, CLS, and INP. #performance #devtools #chrome calendar.perfplanet.com/2025/chrome-...

Been loving NVIDIA's NeMo models recently to complement Whisper for transcription, but the startup felt a bit heavy. So I went on a profiling adventure! github.com/NVIDIA-NeMo/... Turned out to be fruitful… stoked to land a big optimization in NeMO. github.com/NVIDIA-NeMo/...

My talk at @henrihelvetica.bsky.social's SPDY meetup in Toronto is live: www.youtube.com/watch?v=xq2c.... It's pretty rough and unpolished, but I included some fun stories of the history of performance work in Chrome which you likely can't find anywhere else. Slides: docs.google.com/presentation...

The 2025 Web Almanac by HTTP Archive has been officially released! 🚀 We would like to thank all of our contributors from around the globe who made this extensive report possible! Check out the full report here: almanac.httparchive.org

Happy New Year! Join us next Thursday, January 15, "Frameworks for humans in the age of machines" with Rich Harris - @rich-harris.dev PLEASE update your RSVPs if you cannot attend! RSVP: www.meetup.com/web-performa... This is a joint event with @sveltesociety.dev NYC #webperf #wpo #perfmatters

I’ve decided to invest time in learning WebAssembly with the aim of improving the performance of some products I know that WebAssembly isn’t a silver bullet that solves everything, but there are use cases where it can significantly improve a product’s UX #WebPerf #WebAssembly #Performance

When web performance degrades, the impact is immediate. Conversions drop. UX suffers. SEO follows. The problem? These issues are often detected too late.

📣 Nuevo post: Chrome DevTools para depurar el rendimiento de una web Una guía paso a paso de cómo utilizo Chrome DevTools para detectar problemas de Web Performance en una web, así como validar algunas hipótesis joanleon.dev/posts/chrome... #WebPerf #DevTools

🚀 WebPerf Snippets – Major Update ✨ What’s new • Visual ratings 🟢/🟡/🔴 • Clean tables report • Automatic summaries • Issue detection with actionable recommendations • Improved docs with causes, fixes & official links 👉 webperf-snippets.nucliweb.net #WebPerf #CoreWebVitals #JavaScript #DevTools