A long-standing lux.js bug left Event Timing on its 104 ms default, while browser releases improve testing and rendering performance.

Just how much does TTFB matter when it comes to front-end performance?

The new Speculation Rules API is incredibly powerful, but we can do so much more! By taking a layered approach, we can add more progressive functionality.

The TBT Window is the FCP-to-TTI interval used to calculate Total Blocking Time. If FCP or TTI moves, TBT can change even when long tasks do not.

Browse the full CSS Wizardry archive of articles on web performance, Core Web Vitals, caching, CSS architecture, and front-end engineering.

No-Vary-Search lets HTTP caches ignore irrelevant query parameters such as UTM tags, while still keeping meaningful ones like product variants in the cache key.

BCP14 contains RFC 2119, RFC 8174.

Chrome and Firefox are moving to two-week releases, making browser cadence part of how teams interpret RUM and plan performance testing.

Use Gmail’s Message-ID to point Codex or Claude at one exact email and retrieve the complete conversation rather than a plausible result.

LUX Sidecar is a small SpeedCurve RUM plugin that adds browser and navigation context to your real-user performance data.

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

LUX Sidecar adds context to RUM, while browser-tool fixes show why measurement conditions and small debugging details matter.

Safari Technology Preview 250 fixed a subtle Web Inspector bug that overwrote page-authored Cache-Control request headers when the resource cache was disabled.

LUX Sidecar – Your SpeedCurve Companion. GitHub Gist: instantly share code, notes, and snippets.

The 2026 update to my real-world device testing recommendations paints a clearer picture than ever…

I’m a frontend developer, consultant, accessibility auditor, blogger, teacher, and book author from Austria.