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Jacob "kurtextrem" Groß

@kurtextrem.de

885 followers 362 following 103 posts

Staff Performance Engineer @Framer · webperf/UX/AI and the Core Web Vital INP are my interests. ex. gamer · @kurtextrem on other platforms.

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Jacob "kurtextrem" Groß @kurtextrem.de · 03/05/2026

I started migrating the main monorepo at @framer.com to @voidzero.dev's oxlint. Speed difference is day and night. For 420 enabled rules (including typescript-eslint rules), without cache: eslint: 3m58s | 21 GB RAM oxlint: 0m46s | 4.6 GB RAM (oxlint) + 6 GB tsgo 🚀5x faster, 2x less RAM usage

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Jacob "kurtextrem" Groß @kurtextrem.de · 31/10/2025

#PerfNow has incredibly interesting talks. Anyone who's serious about performance should join. Proud that we at @framer.com are sponsors.

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Jacob "kurtextrem" Groß @kurtextrem.de · 17/10/2025

⚛️ReactConf once again mentioned concurrent stores. What if I tell you, we have concurrent external stores today? (kinda) My latest blog post explains: 👉 How to to pair `useSyncExternalStore` with `useDeferredValue` (and `useMemo`) ⚡ Why this can improve UX & INP during hydration

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Jacob "kurtextrem" Groß @kurtextrem.de · 15/09/2025

I don't have a sandbox, but we're using it on prod @ Framer.

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Jacob "kurtextrem" Groß @kurtextrem.de · 25/08/2025

PSA: There's an open bug in React 19.1 that emits a `<link rel="preload">` for every single `<img>` tag on a page when you SSR: github.com/facebook/rea.... This can result in *tons* of preloads that are bad for LCP and also wastes network bandwidth/data.

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Jacob "kurtextrem" Groß @kurtextrem.de · 30/04/2025

The "Performance" tab of DevTools shows compilation & parsing here - important: disable caching to avoid v8's byte cache! The compile hint changes how early the compilation happens. If the main thread stalls while waiting for compilation to finish, the compile hint can have positive impact.

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Jacob "kurtextrem" Groß @kurtextrem.de · 30/04/2025

An easy way to figure out if this might make sense to add for you: Open Chrome DevTools -> 3 dots -> More tools -> Coverage. The files with the least amount of unused functions right after a page load, will gain the most from this.

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Jacob "kurtextrem" Groß @kurtextrem.de · 30/04/2025

Chrome 136+ ships a new V8 version that supports a "compile hint", which makes V8 parse and compile all functions in that file eagerly. Great for entry points – where you know all functions will very likely be used. Less so as 'one weird trick to make all your JS faster'.

In our experiment with popular web pages, 17 out of 20 showed improvements, and the average foreground parse and compile times reduction was 630 ms.

You can trigger eager compilation for the whole file by inserting the magic comment
```
//# allFunctionsCalledOnLoad
```
at the top of the file.

This feature should be used sparingly though - compiling too much will consume time and memory!

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Jacob "kurtextrem" Groß @kurtextrem.de · 02/12/2024

Part 2 of my "How to improve INP" series is for library authors and devs working on React codebases. We'll take a look at how to: ✨ Ensure great INP & UX after user interactions 🚀 Make hydration concurrent 💡 Get non-blocking useEffects, always so that... your site outperforms jQuery instead.

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Jacob "kurtextrem" Groß @kurtextrem.de · 15/11/2024

"Everyone experiences P99" - @anniesullie.bsky.social ... at subway stations, or flaky internet. Understanding & monitoring that experience can make sense. blog.chromium.org/2021/04/digg... #PerfNow

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Jacob "kurtextrem" Groß @kurtextrem.de · 15/11/2024

Closing talk day 2 @ #PerfNow: @anniesullie.bsky.social showing how much time improving CWVs saved. I like how Alex's great talk at the closing of day 1 was a wake-up call and now we get to see the positive side of things as contrast.

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