Can't remember where I stumbled upon a SEO-type guide that was suggesting agent-optimization via a robot.txt-like file llms.txt which lives in the web root and helps agents use your site. Perfect, I t...

Unattributed Navigation Overhead exposes the part of Time to First Byte that Navigation Timing cannot explain, including hidden cross-origin redirects.

AMA. What's a "Micro-Influencer"? Someone with 10K or more followers. Approximately 15% of all Instagram accounts. So I'm a "15 percenter" What's an Instagram? A window on your baby television tha...

This post is another installment of the series dedicated to building sightread.org. Parts 1, 2, 3, 4, 5, 6. I've been using TypeScript (actually JSDoc + tsc --noEmit) as my linter for a while. Well, ...

Practice rhythms in 5/8, 7/8, and 11/8 with flexible beat groupings that make these meters feel natural.

The questions Is rendering large SVGs significantly slower than smaller ones? Is there a cut-off size above which things are terrible? And what if these SVGs were PNGs, just for giggles. To answer t...

Who amongst us has not created a blogging software of some fashion or another? I know I have, many times. My latest (joke-y) attempt was Lizzy.js. The desire to go into a writing mode and don't worry ...

SightRead.org now has quests. Rhythmic Dictation is a new mode where you hear a rhythm and try to identify it.

Stoyan Stefanov calls AI an electric bike for the brain. But he warns it can also lead you straight off a performance cliff.

This is part 4 of a series about hacking on sightread.org with minimal tooling/building and maximum web platform-ing: Part 1: Import JavaScript like it's 2026 Part 2: Maximally Minimal Build Proc...

The speed geek's favorite time of year

In my previous post I described how I set up sightread.org with no build process and modern JavaScript. The goal was raw ES modules, no transpilation, no bundling, just <script type="module"> and we'r...

Get expert insights on Core Web Vitals and performance optimization from an AI specialized in web performance analysis.

Buried at the end of this year's instalment of my semi-annual series on network and device reality is a mystery: multiple, independent data sets from the Web Performance community indicate sites built...

Compression Dictionary Transport became an official IETF Proposed Standard this September (congratulations to Yoav Weiss & Pat Meenan 🎉). If you don't know what they are, I recommend watching Pat's wo...

AI is kinda everywhere! Everyone is shipping AI features or Agents, but few of those systems can reason about the complex reality of performance data. This session is a deep dive story into the jour...

Most developers open Chrome DevTools, check a couple of network requests, maybe refresh the page once or twice — and that's it. I used to do the same. Over time, DevTools became something else entir...

It's been a long, busy year but my friend Faisal and I stayed focused on building BasicRUM. After work, we pushed countless commits from a cozy café in Munich. The important news is that we're wrappi...

This year, Sergey Chernyshev, Eric Goldstein, and Alex Chernyshev - members of the NY Web Performance meetup - decided to collaborate on the future of the UX Speed Calculator tool Sergey created a few...

You've heard it many times - third party content can easily cause an otherwise well performing website to become sluggish and slow. And depending on how this content is loaded, it can also introduce s...

Introduction The Performance Panel is used for detailed investigations on traces captured during page load or during user interactions. It's a critical tool for understanding and debugging performanc...

This is a step-by-step guide on how I use Chrome DevTools (DevTools from now on) to detect Web Performance issues on a website, as well as validate hypotheses to fix some of the problems found. Discl...

Introduction Modern web performance issues often come from delayed rendering rather than network speed. Client-side hydration and heavy JavaScript pipelines can prevent browsers from showing content ...

What is BFCache? The Back/Forward Cache, or BFCache, is a browser mechanism that allows a page to be restored instantly when a user uses the browser's Back or Forward buttons. Unlike a simple HTTP c...

Time-To-First-Byte (TTFB) is a popular performance metric, yet there are many problems and nuances with it. Not only does it have several different definitions, it is usually also a "compound" metric,...

Tales of two pages… What's the difference between these two pages?: https://www.example.com/ https://www.example.com/?utm_source=email I mean they've got different URLs, but many of us would ...

Over the course of 2025, I have completed 100 site speed reviews at DebugBear. This is a free service we offer to trial accounts looking for a brief assessment of their current web performance. Reque...

Even though Cumulative Layout Shift (CLS) has been a well-known metric for about five years now, I still frequently encounter negative scores on major websites during my web performance audits. The m...

A long time ago, in 2014, I did the “A Short History of Performance Engineering” Ignite talk at the Velocity conference (slides and video). A lot of new developments have happened since 2014, so here ...

Optimizing LCP (Largest Contentful Paint) is not just reducing the file size of your images, there's a lot more that goes into optimizing the loading strategy - and you can only grasp where the bottle...

How mainframe-era techniques and native browser APIs outperform modern frameworks The Numbers Before the philosophy, the receipts: Frontend (multicardz.com): 32KB JavaScript bundle (15% of mini...