This article provides information about the changes in Firefox 157 that affect developers. Firefox 157 was released on September 29, 2026.

Gecko: Intent to Ship: CSS Typed Arithmetic

CSS is getting a random() function that lets you set properties with a random value, opening up a ton of interesting creative possibilities. In this article…

Gecko: Intent to Prototype: CSS random() math function

Gecko: Intent to Ship: alpha() relative color function

Gecko: Intent to Prototype: CSS at-rule() function for @supports

RESOLVED (sajidanwar94) in Core - CSS Parsing and Computation. Last updated 2026-08-01.

YouTube video by Firefox for Web Developers

Gecko: Intent to Prototype: CSS Typed Arithmetic

Gecko: Intent to Ship: text-box-trim / text-box-edge

At block parties, backyards and beer halls, an expanded tournament gave immigrant diasporas large and small the chance to revel in support of their home countries.

Gecko: Intent to Prototype: text-box-trim / text-box-edge

Gecko: Intent to Ship: sibling-index() and sibling-count()

Gecko: Intent to Prototype: alpha() relative color function

Gecko: Intent to Prototype: CSS progress() function

Gecko: Intent to Prototype: sibling-index() and sibling-count()

The two federal immigration agents who fired on Minneapolis protester Alex Pretti are identified in government records as Border Patrol agent Jesus Ochoa and Customs and Border Protection officer Raym...