⚡️ Web Performance Artisan at @perfreviews_ | @GoogleDevExpert in #WebTech | @cloudinary Ambassador
Girona, Catalunya
- Tweets 21,524
- Following 4,313
- Followers 12,124
- Likes 46,950
Pinned Tweet
I have published a website with Web Performance Snippets to make it more user-friendly, more orderly, and with a search feature
⚡️💾 webperf-snippets.nucliweb.ne…
#WebPerf #Performance #PerfTools
3
48
206
34,482
One thing I’m experimenting with for a performance audit:
Using RUM data + @debugbear MCP to build synthetic tests based on how the product is actually used
RUM → real user behaviour → MCP → representative synthetic tests
debugbear.com/docs/mcp
#WebPerf #RUM #MCP
3
199
Joan León 🏞️⚡️ retweeted
La #GeeksCAT2026 ja és història, i quina història! ⚡
Sala plena a L'Estació Espai Jove, 10 ponències d'altíssim nivell tècnic, debats sans i retrobaments amb la comunitat tecnològica a Girona.
Obrim fil amb el resum i agraïments 👇🧵
#GeeksCAT #Girona
ALT Foto de grup de l'equip d'organització, suport i els 10 ponents de la GeeksCAT Conf 2026 somrient a l'escenari de L'Estació Espai Jove de Girona al final de la jornada.
2
8
11
657
Joan León 🏞️⚡️ retweeted
Una xarrada de @carlesnunez de rendiment, de les que li agraden al nostre company @nucliweb ☺️
#GeeksCat #GeeksCatConf
2
5
1,372
Joan León 🏞️⚡️ retweeted
We gave Claude Opus 5.5 an article we wrote a few months ago and asked it to turn it into an animation.👇
📖 The Anatomy of a Web Performance Report
calendar.perfplanet.com/2025…
Thanks for the idea, @addyosmani !
#AI #ClaudeAI #WebPerf
1
5
288
Joan León 🏞️⚡️ retweeted
Claude Opus 5.5 drew each frame of this animation in JavaScript. Here's "how browsers work" in 40 seconds.
134
160
2,394
213,904
Joan León 🏞️⚡️ retweeted
AI Reporting Workflow ✨
Turn one WebPerformance Report into:
→ UX & SEO Audits
→ Benchmarks
→ Cross-report correlations
→ Executive summaries
→ Tickets & tasks
→ And much more
WPR Report → AI → Insights → Action
Use ChatGPT, Claude, or Gemini.
Link in comments 👇
1
1
1
177
Joan León 🏞️⚡️ retweeted
🎇 I made a small Chrome extension: a side panel that drives any site's WebMCP tools with Jev!
When you type, on every keystroke it picks the relevant page's tool, fills in the arguments, and tells you how sure it is.
Here it is grocery shopping:
48
90
1,110
75,523
The case against JPEG XL
Investigating JPEG XL's place as a Web image codec, by Gianni Rosato, via @WebPerfReport
giannirosato.com/blog/post/c…
#JPEGXL #JXL #ImagePerf #WebPerf
ALT A dark-themed line chart titled “SSIMULACRA2,” showing BD-Rate (%) versus encoding speed in milliseconds for several image codecs. Colored lines compare codecs including AOM, JPEG XL, aperture-alpha, Iris-WebP, libjxl, SVT-AV1, and libwebp, with labeled data points. Most curves show higher BD-Rate at slower speeds, while some reach negative BD-Rate at faster speeds.
1
3
1,562
Kodak images are old film based images with blur, film grain and lack of resolution. The corpus was then scanned from film to digital using the scanner technology from late 1980s or very early 1990s.
This is not a way to benchmark modern codecs.
If you compare with a high quality digital corpus you will get different numbers.
4
1
23
514
Joan León 🏞️⚡️ retweeted
Kodak images are old film based images with blur, film grain and lack of resolution. The corpus was then scanned from film to digital using the scanner technology from late 1980s or very early 1990s.
This is not a way to benchmark modern codecs.
If you compare with a high quality digital corpus you will get different numbers.
4
1
23
514
Joan León 🏞️⚡️ retweeted
Reminder: Claude Code can test if a skill or plugin actually improves Claude's answers.
> claude plugin eval init
Tell Claude what a good result looks like in your plugin's folder and it writes the test cases for you.
> run claude plugin eval .
99
121
1,772
180,197
Joan León 🏞️⚡️ retweeted
🔮 Built a real-time click prediction right over the DOM using JEV that feels like a crystal ball.
Powered by jev-latest to predict the next clickable element and intent in 345ms per check, highlighting candidate elements on screen.
It's extremely cheap to use and helps predict user intention, hitting 83% accuracy in testing.
Usages that come to my mind:
- Web performance optimization via predictive resource load
- UX Research and testing
- Progressive UI loading based on intention
- Accessibility for reduced motor precision (highlight based on intention allowing to click, for example)
- And probably many more...
2
7
20
1,914
Joan León 🏞️⚡️ retweeted
⚡Featured posts this week:
✨ New ad metrics in CrUX: @alextcone
✨ The case against JPEG XL: Gianni Rosato
✨ Why Spotify Is Not Using Bayesian A/B Testing: Mattias Frånberg, Mårten Schultzberg
✨ International SEO: Barry Adams
🙏 Special thanks to the authors!
#webperf
ALT WebPerformance Report performance email preview highlighting optimization scores, Perf Links, and Core Web Vitals metrics on a colorful gradient background.
1
1
1
244
🔮 He construido una predicción de clic en tiempo real sobre el DOM usando JEV que parece una bola de cristal.
Funciona con jev-latest para predecir el siguiente elemento clicable y la intención del usuario en 345 ms por consulta, resaltando los candidatos en pantalla.
Es extremadamente barato de usar y ayuda a anticipar la intención del usuario con un 83% de acierto en las pruebas.
Usos que se me ocurren:
- Optimización del rendimiento web mediante precarga predictiva de recursos
- Investigación y pruebas de UX
- Carga progresiva de la interfaz según la intención
- Accesibilidad para personas con precisión motriz reducida (resaltar según la intención y permitir el clic, por ejemplo)
- Y seguramente muchos más...
5
6
85
5,693
🤩 Solo digo: Speculation Rules API, preload, prefetch, preconnect.
Con esas ideas, ojo que @PerfReviews_ no te quiera fichar ☺️
1
1
298
Joan León 🏞️⚡️ retweeted
Agent: *screenshots the page*
Agent: *scrolls*
Agent: *screenshots again*
Agent: *clicks the wrong button*
Agent: *screenshots again*
Page with WebMCP: hi, here are the 4 things you can do here, with descriptions
Agent: oh thank god
34
45
1,240
63,207
Joan León 🏞️⚡️ retweeted
Modern Web Guidance v0.0.187 brings new and updated guides and Codex plugin support → goo.gle/4harAXQ
✨ New guides: progress rings, scrollspy nav menus, loading spinners
📝 Updated guidance to avoid bfcache breakage and unwanted inline layout gaps
🔌 Added plugin manifest support for Codex
4
24
247
17,835
Joan León 🏞️⚡️ retweeted
10,000 installs and counting! 📈 We created Modern Web Guidance to bring web platform expertise right into your agent workflows. Have you tried pairing these skills with Chrome DevTools for agents to audit performance and automatically fix code?
Check it out and join 10K+ web developers who are coding smarter → goo.gle/4yEVz1h
22
140
1,072
75,664