New year, new web performance mystery (and it's a huge one): calendar.perfplanet.com/2025/the-cur...

📣 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

I’m starting the year by migrating the webperf-snippets.nucliweb.net project to the latest versions. I’m also improving the documentation and scripts, with better console output. Keep an eye out for upcoming updates #WebPerf #WebPerfSnippets #PerfTools #Performance #DevTools

Marketing: Hello, Joan! Can we add a short video as a background in the hero component? Me: 🫠 #WebPerf #Performance #TrueStories

Our Web Performance Journey guide is live on PerfPlanet Calendar!

Web Performance Calendar day 28 when Ian Duffy shows us how to tame Chrome’s Performance panel: reduce noise, search fast, annotate, use Insights, and customize tracks calendar.perfplanet.com/2025/tips-fo...

Web Performance Calendar day 27 with @nucliweb.net on using Chrome DevTools for fun and profit: inspect heavy files in Network panel, monitor Core Web Vitals, record performance traces, validate optimizations, and more. calendar.perfplanet.com/2025/chrome-...

La propiedad CSS content-visibility puede mejorar significativamente el rendimiento de renderizado, especialmente en páginas con mucho contenido En este post: cómo funciona, un caso real con métricas antes/después, y snippets para auditar joanleon.dev/posts/conten... #WebPerf #Performance #CSS

How to load CSS (fast) calendar.perfplanet.com/2025/how-to-... by @yoavweiss #WebPerf #CSSPerf #Performance #CSS

Web Performance Calendar day 21 with Conor McCarthy and lessons learned from web perf client site reviews calendar.perfplanet.com/2025/insight...

Why Your Server Is Paying for Your CSS Choices dp-lewis.medium.com/why-your-ser... #CSS #WebPerf #ServerPerf

Check out all the revised demos of Grid Lanes in Safari Technology Preview 234! webkit.org/demos/grid3/

Updated de Content-Visibility snippet for Chrome DevTools - Detects existing content-visibility usage - Finds offscreen optimization opportunities - CLS warnings for missing contain-intrinsic-size - Configurable thresholds webperf-snippets.nucliweb.net/Loading/Cont... #WebPerf #PerfTools

About to start a new Web Performance consulting project & I’m really looking forward to it I’m sure I’ll enjoy working on this, and the impact on the client’s conversions should be very noticeable 📈 Performance is where UX and business truly meet #WebPerf #WebPerformance #CoreWebVitals #UX

Web Performance Calendar day 19 with Alex Podelko on how performance engineering has evolved with computing: from mainframes to distributed systems, web/mobile, cloud, AI. Knowing your history may help reduce wheel-reinvention and encourage skills reuse calendar.perfplanet.com/2025/a-short...

Lazy loading out-of-viewport images can make the main content on your website load faster. ⬇️ Learn how in this video. www.youtube.com/watch?v=CPJf...

Major update to the CSS Media Queries Analysis Snippet with a Performance Impact Analyzer It calculates the REAL cost of desktop-only CSS on mobile: 📉 Core Web Vitals Impact 💰 Estimated Conversion Lift e.g.: Fixing 30KB of unused CSS 180ms faster load and up to 1.8% conversion boost

I really love the page transition on PerfPlanet’s Calendar 🤩 Smooth details like this make a big difference in web performance and UX. #WebPerf #PerfPlanet #UX

⚡Featured posts this week: ✨ Timeline of web features and browser support: @rviscomi.dev ✨ Fast by Default: @denodell.bsky.social ✨ Analyzing CSS Media Queries to Optimize Perf: @nucliweb.net ✨ What was new in web perf in 2025: @mattzeunert.com 🙏 Special thanks to the authors! #webperf

🤩We just opened the Public Preview of our Reporting as a Service (RaaS) platform before the general release. Users from different countries are already accessing their personal Boards. Explore the platform by getting your own report: 👉 webperformancereport.com #webperf

Half a year ago, I published a pretty long paper about JPEG XL: arxiv.org/abs/2506.05987 I am happy to see that section 11.1 is already outdated!

Chrome DevTools' ~4 GB prompt is your Local LLM onboarding It's the required download for Zero-Exfiltration AI (client-side inference) Benefits: Maximum Privacy (data stays on device) + Low-Latency Debugging Download the weights to use the future of DevTools #DevTools #LLM #OnDeviceAI #Debugging

chrome-devtools-mcp v0.11.0 🎉 Features - emulation: add geolocation emulation tool - integrate DevTools issues into the console tools - support --user-data-dir github.com/ChromeDevToo... #DevTools #mcp #ai #Chrome

Added a new request stats view to the DebugBear page speed test result! Try it for free here www.debugbear.com/test/website...

I wrote a little thing for the HTML Hell advent calendar from @matuzo.at — but on a good improvement to HTML rather than a hellish thing 🙂 Improvements to the Speculation Rules API, which allows you to (now more easily) prefetch and prerender HTML pages: htmhell.dev/adventcalend...

- Use a <picture> tag for semantic HTML - Sure, I’ll do it #SendMeCoffee 🫠

Análisis de Media Queries en CSS para Optimizar el Rendimiento joanleon.dev/posts/analis... 🇬🇧 version in thread #WebPerf #CSS #WebPerfSnippets #PerfTools #DevTools

New in Chrome DevTools in Chrome 144: we now show the Adopted Style Sheets in the Elements tree.

December is here (in a few hours in my timezone), which means the Web Performance "Advent" Calendar is back for its... 17th Edition! One article a day in the month of December. Be a part of it and contribute an article: calendar.perfplanet.com/contribute/

📣 New WebPerf Snippet Analyze all @media rules in CSS to identify classes and properties targeting viewports bigger than a specified breakpoint. Results are grouped by inline CSS and external files, with byte size estimates for potential mobile savings. #WebPerfSnippets #WebPerf

Avui toca aprendre accessibilitat a @a11yconf.bsky.social , i amb el luxe de poder fer-ho a Girona ☺️ Hoy toca aprender accesibilidad en @a11yconf.bsky.social, y con el lujo de poder hacerlo en Girona ☺️ #a11yConf #a11yConf2025 #a11y #accesibilidad #accessibilitat #accessibility

As @developer.chrome.com DevTools user, I’ve earned my sticker badge 😎 #DevTools

📣 Updated my Resource Hints snippet for @chromedevtools.bsky.social Now detects common mistakes like: ❌ <link rel="preconnect dns-prefetch"> ❌ Non-standard rel values Perfect for auditing preload, prefetch, preconnect, etc webperf-snippets.nucliweb.net/Loading/Reso... #WebPerf #PerfTools

With @chromedevtools.bsky.social, we can streamline Web Performance Debugging with the help of the AI assistant #WebPerf #PerfTools #PerfDebugging

This is quite the speed test from @cloudflare.social + I get a CSV of the details. Like getting a fortune cookie after dinner. Raw data but still cool to have. speed.cloudflare.com

⚡Featured posts this week: ✨ WebPerf Report on SPDY STREAM: @henrihelvetica.bsky.social ✨ WordPress 6.9 Perf Landings: @weston.ruter.net ✨ I Built the Same App 10 Times: @cheddybop.bsky.social ✨ Start building with Gemini 3: @officiallogank.bsky.social 🙏 Special thanks to the authors! #webperf

Aprendiendo qué es Firebase Studio de la mano del gran @carlosazaustre.bsky.social en DevFest Barcelona 2025 #DevFestBCN2025

Dr. @guaca.bsky.social explains the diagnosis with @debugbear.com of our symptoms at DevFest Barcelona 2025 #DevFestBCN2025 #WebPerf #PerfTools #DevFest

Nuevo post "Más Allá de INP: LCP y el 90% invisible del rendimiento" de la serie de Long Animation frames API (LoAF) joanleon.dev/posts/loaf/m... #WebPerf #Performance #LoAF #LCP #CoreWebVitals

I've updated the WebPerf Snippet "Find non Lazy Loaded Images outside of the viewport" to list images without loading="lazy". Now it shows: - Total number of images - Total file size - Individual details: URL, resolution & file size #WebPerf #WebPerfSnippets #PerfTools

Obs.js: context-aware web performance for everyone csswizardry.com/Obs.js/demo/ by @csswizardry.com #WebPerf #PerfTools #Performance #WebPerfSnippets

Dark mode = On

Send me some coffee 🫠 #WebPerf #WebPerfEngLive

TIL about the HTML Size Analyzer from DebugBear. Great for finding sneaky Data URIs or large payloads of JSON in your pages: www.debugbear.com/html-size-an...

✨ SPDY STREAM 017 ✨ featuring @verlok.bsky.social of Speed Kit joins us to discuss the Interaction to Next Paint (INP) metric and how you can avoid the most common errors that degrade UI responsiveness. JOIN US! 📆 Wednesday Nov 19th ⏰ 11am EST* (special time), 5pm CET 🔗 youtube.com/live/fTGm2gW...

Reminder: our next meetup is this Wednesday! Join live for access to Q&A and general chat! #webperf

I reached peak performance using @chromedevtools.bsky.social's Performance panel! #DevBadges developers.google.com/profile/badg...

Call for Speakers for @codemotion.bsky.social Madrid 2026 is open and I've just submitted 3 sessions! (2 talks and 1 workshop) sessionize.com/codemotion-m... #CodeMotion

HTML parsing speed depends a lot on how powerful the device that's visiting the website is. When I measure parse time on my laptop it takes under 7 milliseconds to process one megabyte of HTML. But on a low-end Android phone it takes 88 milliseconds! www.debugbear.com/blog/html-pa...