The browser APIs you're shipping libraries to replace with Kilian Valkhof

LogRocket — Thu, 02 Apr 2026 08:00:00 -0400

Most developers reach for date-fns or Moment.js without realizing the browser already ships a powerful string formatting library called the JavaScript Intl API. Killian Valkhof, creator of Polypane, walks through how locale-aware date formatting, currency formatting, the Segmenter API, and the Collator API can replace heavy npm dependencies, with support for over 7,000 locales baked right into every evergreen browser since 2017.

Resources

INTL: The best browser API you’re not using | Kilian Valkhof: https://www.youtube.com/watch?v=mhzJ1UFlRjw

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Chapters

00:00 Introduction — Browser APIs & the Intl API
01:00 Why Developers Overlook Internationalization
02:30 What the Intl API Actually Is (It's a Formatting Library)
04:00 7,000 Locales Built Into Every Browser
06:00 What Intl Does NOT Do — It's String Output Only
07:00 date-fns, Moment.js, Luxon, and Numeral.js Compared
09:00 Why the Segmented Rollout Slowed Adoption
11:00 Currency Formatting and Locale Trust Signals
13:00 The Worst Under-Used API in the Browser
16:00 How Browser Specs Have Evolved Since HTML5
18:30 Dialogue, Popover, Anchor Positioning — New Primitives
23:00 The Top Layer and Z-Index Problems Solved
25:00 WebGPU, WASM, and Native API Trends
27:30 The Easiest Way to Start Using Intl Today
31:00 Collator, Segmenter, and List Format APIs
32:00 Wrap-Up and Where to Find Killian's Full Talk Special Guest: Kilian Valkhof.