Safari Technology Preview 253 landed September 23 with a theme worth naming: features that remove hierarchy-shaped restrictions. Timelines and selector functions stop insisting on ancestry, and text follows any path you could draw.

Published 2026-09-23: https://webkit.org/blog/18357/release-notes-for-safari-technology-preview-253/

Highlights from the notes

  • Style-originated scroll timelines can now match globally: define a timeline outside the target hierarchy or through timeline-scope, and animations outside that ancestry still pick it up.
  • sibling-index() and sibling-count() work inside container query conditions too, which closes the distance between layout state and decision.
  • SVG textPath gains the SVG 2 path attribute, so text can follow an inline path without referencing a separate element.
  • Web Inspector adds network throttling of the inspected page, so performance work gets a built-in constraint dial.

Also in the batch

The offscreen API reaches extension service workers in this preview, and the JavaScript section is pleasant: BigInt support in Intl.PluralRules select and selectRange, plus a faster multiplication algorithm for very large integers. A gacor release for anyone keeping score on animation correctness; an impressive batch of scroll timeline edge fixes rides along.

If you drive animation off scroll state, this is the release to retest your timeline scopes in; the fixes are subtle before they are visible.