Joan León
@nucliweb.net
⚡️ Web Performance Artisan at @perf.reviews | Google Dev Expert in Web Tech | Cloudinary Ambassador | ❤️ Image Optimization | Girona
A letter from @addyosmani.bsky.social arrived today, thanking me for my work on Agent Skills. I got in through web performance and stayed for the rest. Thinking about contributing to open source? Start small. Docs and honest reviews count. github.com/addyosmani/a...
Web performance is a marathon, not a sprint. Ship the fastest site today and in two weeks a third-party script, an unoptimised image or a CDN change will have quietly undone it. Optimising without monitoring doesn't last. 🧵 #WebPerf #RUM #CoreWebVitals
While some people laughed about the number of dependencies in the JS world, others worked to improve the ecosystem (like @e18e.dev). Now many of my open source projects have around 20 packages in node_modules, including transitive dependencies.
⚡Featured posts this week: ✨ Is your site agent-ready?: @cloudflare.social ✨ Measuring soft navigations: @tunetheweb.com and @mmocny.com ✨ Reading a performance profile: @nucliweb.net ✨ The Absolute State of Management: @infrequently.org 🙏 Special thanks to the authors! #webperf
We got a few new individual sponsors recently in @e18e.dev - thank you to those of you who are supporting us 🙏 Getting sponsorships for a community is much harder than for a popular web app or dev tool. Every little helps. If you'd like to help us improve perf for all of us, check out our OC 🩵
e18e - Ecosystem Performance - Open Collective
The e18e community has the aim of improving performance of tooling and packages in the JavaScript ecosystem.
opencollective.com
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
Reading a Performance Profile: Field Guide
An interactive field guide to the Chrome DevTools Performance panel: waterfall, flame chart, LCP, CLS, INP, and the Insights panel.
perf.reviews
The curse of web performance - once you know it, you can’t unknown it and I see performance issues on the sites I visit too and can’t help it but open DevTools often as well. I was even thinking for creating a podcast-style Meet4SPEED YouTube channel looking at websites and improving them.
Joan León@nucliweb.net · 2w agoAn 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
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
I'm testing the @debugbear.com MCP with Claude Code, and my first impression is that combining DebugBear's great tools with the power of AI Agents is awesome for creating executive and detailed technical reports... #WebPerf #PerfTools #AI #WebPerfAI
I've been running #Antigravity Skills in real projects and the YAML frontmatter does much more than the docs show. kind: subagent + restricted tools + the right model per task. That trio makes agent behavior predictable and keeps costs in check. joanleon.dev/en/antigravi... #AI #AgentSkills
Antigravity Skills: advanced YAML frontmatter configuration | Joan León
The kind, model, temperature, max_turns and tools fields in SKILL.md frontmatter let you precisely control how each agent runs in Antigravity. A practical guide to the extended fields that Google hasn...
joanleon.dev
Friend: Hey, Joan, can you give us a hand? Me: Sure, send me the URL DevTools: It takes nearly 3 seconds to load the WordPress plugins Me: 🫠
Este fin de semana he podido conocer a Edu, ver su Keynote en @commit-conf.com, y conversar con él, y tengo muy claro que quiero leer ese libro 📖
Edu Ferro (eferro) 🇵🇸@eferro.net · 2mo agoLlevo 25+ años construyendo equipos y veo el mismo patrón: al principio entregáis rápido, pero cada feature, integración y decisión va sumando peso. Hasta que casi toda la energía del equipo se va en sostener lo que ya existe.
Gracias @commit-conf.com por darme la oportunidad de compartir con la comunidad Estas son las slides de la charla slides.com/joanleon/pat... #CommitConf #WebPerf
⚡Featured posts this week: ✨ Zero Trust Implementation Guidelines: National Security Agency ✨The Website Specification: @joost.blog ✨Agent Skills: @addyosmani.bsky.social @oreilly.bsky.social ✨Lighthouse agentic browsing scoring: @developer.chrome.com 🙏 Special thanks to the authors! #webperf
AI coding tools are powerful at writing code, but they can't inspect execution in a live browser. The stable 1.0 release of Chrome DevTools for agents provides your AI assistant with the visibility it needs to verify, debug, and optimize code in real time → goo.gle/42K7Rrl #GoogleIO
“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 👇
Aun estás a tiempo de apuntarte a esta formación para detectar problemas de rendimiento web con agentes de IA #WebPerf #IA #MCP
Joan León@nucliweb.net · 3mo agoEl 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
This is why the Chrome DevTools MCP is a game-changer. The agent applies a fix, reloads ignoring cache, runs a Lighthouse audit, and checks the score to iterate on the next failure. Fully automated and deterministic. #AgenticDev #WebDev #AI
I think I may have found a memory leak in LinkedIn A single browser tab was consuming 6 GB of RAM just from leaving the feed open for a while Possible causes: • client-side state leaks • excessive caching • unreleased media resources • runaway DOM growth Performance is a feature #WebPerf
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
Browsers Treat Big Sites Differently
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
¿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
Joan León@nucliweb.net · 3mo agoEl 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
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
PerfReviews Insights — Web Performance Analyzer
Analyze any website and get an instant performance report: images, videos, third-party scripts, and page weight.
perf.reviews
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
⚡Featured posts this week: ✨ Store Speed and Conversion: @krzksz.bsky.social ✨ Prepare your Single Page Apps: @tunetheweb.com & @mmocny.com ✨ SEO is sitting in the wrong room: @dias.social ✨ Orchestration without hallucination: @nucliweb.net 🙏 Special thanks to the authors! #webperf
✨ New blog post by me: All about @calibreapp.com’s new UX Rating metric and how it categorises overall user experience quality and distills into something everyone can understand. You’ll learn how it works and why it’s a powerful paradigm for team focus. calibreapp.com/blog/ux-rating
UX Rating: How many of your users are having a good time? | Calibre Blog
UX Rating tells you what share of your users are having a good experience — and where to look when they’re not.
calibreapp.com
WebPerf Snippets meets AI agents: Orchestration without hallucination slides.com/joanleon/web... #WebPerf #WebPerfSnippets #PerfTools
WebPerf Snippets meets AI agents: Orchestration without hallucination
WebPerf Snippets evolved from manual DevTools scripts into an open-source project. Now, it explores a nervous question: Can AI help with web performance? The answer is yes, provided the LLM doesn't m...
slides.com
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
WebGPU: the browser's new performance engine | Joan León
WebGPU exposes the GPU directly to the browser, opening new possibilities for intensive processing: images, video, ML, and more.
joanleon.dev
Join us tomorrow for two great talks from Alfonso Moure and @nucliweb.net ! #webperf All details at... performanceobserver.dev
PerformanceObserver: A virtual web perf meetup
Join the PerformanceObserver virtual performance meetup to get all the latest web performance news and hang out with the community.
performanceobserver.dev
