Temporal reached Stage 4

[...] Temporal reached Stage 4 in the TC39 staging process, which means it will be part of the next annual ECMAScript specification (ES2026). However, you don't need to wait until then - you can use it today!

Temporal is already supported across:

• Firefox v139 (since May 2025)
• Chrome v144 (since January 2026)
• Edge v144 (since January 2026)
• TypeScript 6.0 Beta (since February 2026)
• Safari (Partial Support in Technology Preview)
• Node.js v26 (TBC)

[bloomberg.github.io/js-blog/post/temporal]

Though, according to the list of finished proposals, temporal will not be part of ES2026 but of ES2027. The expected publication year was specifically updated to 2027.

Resources:

• developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Temporal
• caniuse.com/temporal
• github.com/tc39/proposal-temporal
  • github.com/tc39/proposal-temporal/commit/06d3e081706ed2adef95b7e9dbb5b6e6f5e638a2

Newish Firefox Features

• Revamped Profile UI
  • support.mozilla.org/kb/profile-management
• Tab Groups
  • blog.mozilla.org/en/firefox/tab-groups-community
  • support.mozilla.org/kb/tab-groups
• Vertical Tabs
  • blog.mozilla.org/en/firefox/vertical-tabs-and-the-firefox-community
  • support.mozilla.org/kb/use-sidebar-access-tools-and-vertical-tabs
• Translations
  • support.mozilla.org/kb/website-translation
• Multi-Account Containers
  • addons.mozilla.org/firefox/addon/multi-account-containers
• uBlock Origin
  • addons.mozilla.org/firefox/addon/ublock-origin
  • github.com/gorhill/uBlock
  • github.com/gorhill/uBlock/wiki/uBlock-Origin-works-best-on-Firefox

ECMAScript 2025 published

ECMAScript 2025 has been released.

• ecma-international.org/news/ecma-international-approves-new-standards-11
• github.com/tc39/ecma262/releases/tag/es2025
• 262.ecma-international.org/16.0
• ECMAScript Links

The following proposals have reached Stage 4 and are part of ECMAScript 2025:

• Duplicate named capture groups
  • [MDN] Named capturing group: (?<name>...)
• New Set methods
  • [MDN] Set.prototype.intersection()
  • [MDN] Set.prototype.union()
  • [MDN] Set.prototype.difference()
  • [MDN] Set.prototype.symmetricDifference()
  • [MDN] Set.prototype.isSubsetOf()
  • [MDN] Set.prototype.isSupersetOf()
  • [MDN] Set.prototype.isDisjointFrom()
• RegExp Modifiers
  • [MDN] Modifier: (?ims-ims:...)
• Import Attributes
  • [MDN] Import attributes
• JSON Modules
  • [MDN] Import attributes
• Sync Iterator helpers
  • [MDN] Iterator.from()
  • [MDN] Iterator.prototype.drop()
  • [MDN] Iterator.prototype.every()
  • [MDN] Iterator.prototype.filter()
  • [MDN] Iterator.prototype.find()
  • [MDN] Iterator.prototype.flatMap()
  • [MDN] Iterator.prototype.forEach()
  • [MDN] Iterator.prototype.map()
  • [MDN] Iterator.prototype.reduce()
  • [MDN] Iterator.prototype.some()
  • [MDN] Iterator.prototype.take()
  • [MDN] Iterator.prototype.toArray()
• Promise.try
  • [MDN] Promise.try()
• Float16 on TypedArrays, DataView, Math.f16round
  • [MDN] Float16Array
  • [MDN] DataView.prototype.getFloat16()
  • [MDN] DataView.prototype.setFloat16()
  • [MDN] Math.f16round()
• RegExp.escape
  • [MDN] RegExp.escape()

Most of these new features have already landed in all the important browser engines. Check their compatibility before using them.

What about Temporal? It is still on Stage 3 and thus not part of ECMAScript 2025. There is currently only one conforming implementation (Spidermonkey, released in Firefox 139), but the ECMAScript process requires at least two conforming implementations in order to reach Stage 4. Temporal will likely be part of ECMAScript 2026.

Temporal shipped in Firefox 139

Temporal has shipped in Firefox 139.

• github.com/tc39/proposal-temporal
• mozilla.org/firefox/139.0/releasenotes
• spidermonkey.dev/blog/2025/04/11/shipping-temporal
• caniuse.com/temporal

Thank you, André!

Interop 2025 announced

Interop 2025 is a cross-browser effort to improve the interoperability of the web — to reach a state where each technology works exactly the same in every browser.

[wpt.fyi/interop-2025]

Resources:

• github.com/web-platform-tests/interop
• github.com/web-platform-tests/interop/tree/main/2025
• wpt.fyi/interop-2025

Announcements by contributors:

• hacks.mozilla.org/2025/02/interop-2025
• web.dev/blog/interop-2025
• webkit.org/blog/16458/announcing-interop-2025
• blogs.windows.com/msedgedev/2025/02/13/microsoft-edge-and-interop-2025
• igalia.com/2025/02/13/Interop-2025
• bocoup.com/blog/interop-2025