# Cross-Browser September Updates Accelerate Baseline Standardization for Web Features Major releases across Chrome, Firefox, and Safari bring critical CSS and JavaScript capabilities to Baseline. - **Source:** [web.dev](https://web.dev) - **Published:** 2026-10-02 - **Topic:** [Software & Engineering](https://brifing.si/c/engineering) - **Original article:** - **On Brifing:** https://brifing.si/s/b6dbf582-6a99-42c7-975a-a0ad1e26ad65 ## New Bi-Weekly Release Cadence Browser vendors began bi-weekly release cycles, delivering Chrome 153 and 154 alongside Firefox 155, 156, and 157 in a single month. Combined with Safari 27, this release momentum pushed numerous CSS, HTML, and JavaScript capabilities directly into the Baseline Newly Available status across the ecosystem. ## Advanced CSS Math and Color Firefox 155 enabled the progress math function alongside Safari 27, allowing fluid calculations mapped across viewports with optional no-clamp keywords. Concurrently, the alpha relative color function from CSS Color 5 reached complete interoperability across Chrome, Firefox, and Safari, streamlining contextual opacity adjustments while preserving original color spaces. ## Cascade and Theme Enhancements Safari 27 introduced support for the revert-rule keyword, permitting property values to roll back as if the specific rule were absent. Additionally, the light-dark function expanded beyond color values to accept images and gradients, achieving universal support across all major engines for responsive theme-based visual switching. ## Layout Stability and Typography Scroll anchoring and overflow-anchor properties arrived in Safari 27, preventing unexpected content jumps during DOM mutations above viewports. For typography, CSS Fonts 4 standardized font-width over font-stretch, gaining full descriptor and property coverage across Chrome 154, Firefox 155, and existing Safari implementations to enter Baseline status. ## Responsive Media Optimization Safari 27 added support for sizes auto on lazy-loaded images, enabling engines to pick optimal srcset sources based on rendered element width. This capability joined existing Chrome and Firefox implementations, establishing universal browser support for automated responsive image resource selection without complex manual media query definitions. ## DOM and State Management Standardization reached runtime APIs with Safari 27 adding animation properties to TransitionEvent and AnimationEvent interfaces, async iterable streams, and transferable streams. Developers gained the maxAge option in cookieStore.set for duration-based persistence, while base-select appearance expanded customizable select menu styling into Safari alongside Chrome. ## Declarative Permissions and Performance Chrome 153 introduced camera and microphone capability elements, offering declarative user-activated capture triggers that avoid script-driven prompts. Concurrently, Safari 27 shipped the Service Worker Static Routing API, allowing install-time route declarations via addRoutes to bypass service worker startup overhead and fetch directly from network paths. ## Future Browser Beta Capabilities Upcoming releases signal rapid platform expansion across upcoming beta channels. Chrome test tracks are previewing JPEG XL decoding, deferred module evaluation, and random functions. Meanwhile, Safari betas are refining grid alignments and picker styling, underscoring continuous cross-vendor investment in modern standardized web platform infrastructure. ## Sources covering this story - https://web.dev/blog/web-platform-09-2026?hl=en — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._