Introducing Opportunities & Experiments: Taking the Guesswork out of Performance - WebPageTest Blog

Unveiling the new WebPageTest UI - WebPageTest Blog

If you haven’t seen it yet, the new redesign of WebPageTest is lovely!

The Main Thread Is Not Yours — Den Odell

Every millisecond you spend executing JavaScript is a millisecond the browser can’t spend responding to a click, updating a scroll position, or acknowledging that the user did just try to type something. When your code runs long, you’re not causing “jank” in some abstract technical sense; you’re ignoring someone who’s trying to talk to you.

This is a great way to think about client-side JavaScript!

Also:

Before your application code runs a single line, your framework has already spent some of the user’s main thread budget on initialization, hydration, and virtual DOM reconciliation.

I Built the Same App 10 Times: Evaluating Frameworks for Mobile Performance | Loren Stewart

A very, very deep dive into like-for-like comparison of JavaScript frameworks. The takeaway:

Nuxt demonstrates that established “big three” frameworks can achieve next-gen performance when properly configured. Vue’s architecture allows competitive mobile web performance while maintaining a mature ecosystem. React and Angular show no path to similar results.

And the real takeaway:

Mobile is the web. These measurements matter because mobile web is the primary internet for billions of people. If your app is accessible via URL, people will use it on phones with cellular connections. Optimizing for desktop and hoping mobile is good enough is backwards. The web is mobile. Build for that reality.

It’s time for modern CSS to kill the SPA - Jono Alderson

SPAs were a clever solution to a temporary limitation. But that limitation no longer exists.

Use modern server rendering. Use actual pages. Animate with CSS. Preload with intent. Ship less JavaScript.

I’m more proud of these 128 kilobytes than anything I’ve built since | by Mike Hall | Jul, 2025 | Medium

I don’t normally link to articles on Medium—I respect you too much—and I do wish this were written on Mike Hall’s own site, but this is just too good not to share.

And don’t dismiss this as a nostalgiac case study from the past:

At no point did the constraints make the product feel compromised. Users on modern devices got a smooth experience and instant feedback, while those on older devices got fast, reliable functionality. Users on feature phones got the same core experience without the bells and whistles.

The constraints forced us to solve problems in ways we wouldn’t have considered otherwise. Without those constraints, we could have just thrown bytes at the problem, but with them every feature had to justify itself. Core functionality had to work everywhere, and without JavaScript crutches proper markup became essential.

This experience changed how I approach design problems. Constraints aren’t a straitjacket, keeping us from doing our best work; they are the foundation that makes innovation possible. When you have to work within severe limitations, you find elegant solutions that scale beyond those limitations.