Delete your 'is-transitioning' class

Published 9 February 2026 · covers January 2026 · 1 Cleared·1 Skip

January was one release wide. Firefox 147, on 13 January, closed out all seven of the month’s arrivals by itself; nothing else moved. Four of the seven are the root-font versions of existing length units, full marks everywhere and nothing to do with them. The Navigation API reached Baseline the same day, but it is JavaScript, and this letter’s beat is CSS and HTML; it lives in the archive links below. The deletion this month belongs to everyone already running view transitions.

01Cleared

`:active-view-transition`

New this month, 13 January 2026

A pseudo-class that matches the root element while a view transition is running, and stops matching when it settles. Chromium has shipped it since May 2024; Firefox 147 was the last browser in.

Delete: the script that adds a marker class to the root before document.startViewTransition() and removes it when the transition finishes, just so your stylesheet can tell a transition is underway.

CSS · before after

−/* a script toggles this class on <html> */
−.is-transitioning .toolbar { pointer-events: none; }

+/* the selector tracks the transition itself */
+html:active-view-transition .toolbar { pointer-events: none; }

One seam. In a browser too old to know this pseudo-class, the selectors spec makes any selector list containing an invalid selector invalid, whole. Appended to an existing comma-separated rule, :active-view-transition takes the other selectors down with it. Give it its own block, or wrap it in :where(), which parses forgivingly. Done that way, failure is graceful twice over: the rule never matches, and a browser without view transitions has no transition to style anyway.

The four desktop stable runs pass the feature’s tests without exception. Neither Android runner produces a number worth reading: Chrome Android fails the suite’s reftests wholesale at the same engine version that passes on desktop, a known harness fault, and Firefox Android has not been tested publicly since February, when this implementation was four weeks old and still failing its tests. If current Firefox on Android is broken here, the cost is transition styles not applying, the graceful end of wrong. Usage is early, about one page load in ninety thousand, which is also the audience: no view transitions, nothing to delete yet.

02Skip

`animation-composition`

Safe everywhere as of 4 January 2026

Skip, unless you run two animations against the same property of the same element. Then this is for you: it decides whether the second animation replaces the first, the default, or adds to it, or accumulates with it.

It finished its 30 months of support on 4 January with a perfect score in every current stable run, and Chrome’s developer site gave it a dedicated write-up, more promotion than a property this situational usually gets. Hence the printed verdict: in most stylesheets two animations never meet on one property, so there is nothing to delete and nothing to start. Where they do meet, it works everywhere today.

That was January: one release, one deletion, and a clearing shelf with nothing on it that needs removing.

Deleted something because of this? Got a correction? hello at cleared dot page. I read every one.