v0.1.31125 Sep 2026·Rendering, JavaScript & JIT, Media, Tabs & interface

Text now lines up with the reference browser's to a fraction of a percent

A follow-up to 0.1.310 that closes the last visible gap in how text is measured. Most fonts store kerning (the small tightening between letter pairs like A and V, or T and o) in many separate tables, and the engine only ever read the first one, so almost every line of text came out about one percent wider than in the reference browser. It now reads all of them: across every size from 12 to 48 pixels, the macOS system font now lands within a sixth of a percent of the reference browser on average. Pages that measure their own text with scripts (menus that hide what does not fit, "Read more" clamps, carousels) now get the real widths instead of an estimate, so they make the same decisions they make in the reference browser. And a handful of missing web features arrived, including Atomics, Web Locks and View Transitions.

Parity with the reference browser

74overall, as of v0.1.343

Web APIs / DOM surface42

Security architecture66

GPU / graphics acceleration68

DevTools / extensions72

Networking85

Media85

Accessibility85

Real-world site compatibility99

HTML parsing100

CSS parsing + selectors100

Layout: block / flex / grid / tables / writing-modes100

Paint + visual100

JavaScript language100

JavaScript performance (JIT)100

HTML parsing100

What changed 5 changes

Rendering	Kerning now works for real fonts. Fonts keep their letter-pair tightening in many separate tables and the engine only read the first, so pairs like AV, To and We were never tightened and text ran about one percent wide of the reference browser at every size. With every table read, the macOS system font now matches the reference browser's text width to within 0.16% on average (it was 0.98%), and the same fix reaches every other font that kerns this way.
Tabs & interface	Scripts that measure text get the real answer. A page's own scripts used to receive an estimate of how wide text is, so a menu that hides the tabs that do not fit, a "Read more" cut-off or a carousel could size itself wrongly. They now measure with the actual fonts, before the page has even painted: a navigation bar that keeps five tabs in the reference browser now keeps the same five here.
Rendering	Labels that must not wrap stay whole when a row runs out of room. A row of links set not to wrap used to squeeze each link down to its first word, with the rest of the label running into the next link. Each label now keeps its full width, as in the reference browser.
Media	New web features: Atomics (a core part of the JavaScript language that was missing), Web Locks (lets a site coordinate work between its tabs), View Transitions (sites that animate between states now run their update, as an instant change), and the shared media interface that video players check for.
JavaScript & JIT	Pages with hot JavaScript loops start faster: the built-in compiler no longer writes out a full listing of every piece of code it compiles into the browser's log.