Published: September 28, 2026
Welcome to the monthly Baseline digest. In this edition, explore web platform features that reached Baseline Newly available and Baseline Widely available status during August 2026, alongside articles and resources shared by the web developer community.
Modern Web Guidance as a starting point for token skills
Brecht De Ruyte examined how Google's Modern Web Guidance skill set helps AI coding agents write current, Baseline-aware CSS and HTML instead of relying on outdated patterns. The post walks through pairing Modern Web Guidance with custom design token skills to maintain design system consistency while respecting modern platform standards. For more information, see Modern Web Guidance as a starting point for my own token skills: getting agents to write better CSS.
Baseline Newly available features
The following features became supported across all core browser engines in August 2026 and are now Baseline Newly available.
:paused CSS pseudo-class
The :paused pseudo-class matches playable media elements, such as <audio>
and <video>, whenever playback is paused. It also matches media elements that
have loaded but have not yet begun playing. This distinguishes paused playback
from transitional states such as buffering or seeking, allowing media player
controls and surrounding UI to reflect playback states directly in CSS. For more
information, see the MDN documentation for
:paused.
sibling-count() CSS function
The sibling-count() function returns an integer representing the total number
of sibling elements that share a parent element, including the element itself.
Unlike counter(), which returns a string formatted for generated content,
sibling-count() resolves to an integer that can be used directly in math
calculations with calc(). This allows child elements to calculate proportional
layout dimensions, such as column widths, based on their total sibling count
without requiring JavaScript or fixed styles. For more information, see the MDN
documentation for
sibling-count().
Baseline Widely available features
The following feature reached Baseline Widely available status in August 2026, meaning it has been supported across all core browser engines for 30 months and is safe to use without polyfills.
Declarative Shadow DOM
Declarative Shadow DOM lets you define shadow roots directly in HTML markup
using the <template> element with the shadowrootmode attribute set to open
or closed. This removes the need to attach shadow roots with JavaScript
through Element.attachShadow(). It enables server-rendered web components to
render with their encapsulated styles on initial load without flashes of
unstyled content (FOUC), while remaining parseable by search engines and clients
without JavaScript. For more information, see the MDN documentation for
shadowrootmode.
Wrap-up
If a Baseline update or community post was missed, let the team know so it can be included in an upcoming edition. If you have questions or feedback about Baseline, file an issue on the issue tracker.