Apple's latest WebKit preview fixes a cluster of CSS Grid sizing bugs and brings cross-fade() in line with the spec — the kind of quiet correctness work that decides whether a layout renders the same in Safari as it does everywhere else.
Apple shipped Safari Technology Preview 255 on November 2, 2026, and while the headline from mainstream coverage is the usual "bug fixes and performance improvements," the WebKit changelog underneath is a useful snapshot of where Safari's CSS engine still diverges from Chromium and Firefox — and where it just stopped. Grid intrinsic-sizing bugs, a table percentage-height regression, and a cross-fade() implementation that finally matches the CSS Images Level 4 spec all landed in this build. None of it is glamorous, but it's exactly the layer of correctness that teams depend on when they commission iOS app development work that leans on WKWebView to render part of a native app's interface — WebKit is the one rendering engine every iOS browser and in-app web view is required to use, so a Safari-only Grid bug is also a WKWebView bug, full stop.
The official release notes cover WebKit changes between build 322011 and 323397, and the CSS section is dense with sizing fixes rather than new features. Three Grid bugs stand out: min-width: max-content was being ignored when computing the min-content contribution of a percentage-width replaced element (an <img> or <video> sized by percentage inside a grid cell); Grid's intrinsic-width computation wasn't resolving auto-fill repetitions against the container's own min/max size, which could under- or over-count columns; and Grid column sizing was resolving percentage row heights against the inline size instead of the block size when estimating row sizing — a mismatch that's invisible until a percentage-height grid row ends up a completely different height in Safari than in Chrome.
Outside Grid, the fix list includes box-sizing: content-box being ignored for percentage-height display: table elements (padding was silently dropped from the height calculation), font-family: initial behaving like inherit instead of resolving to the actual initial value, and cross-fade() now matching both the CSS Images Level 4 specification and the behavior already shipped in Chromium and Firefox. There's also a correctness fix to how the Styles panel accounts for !important declarations inside a CSS @layer rule when computing which rule wins — a devtools-side fix, but one that matters if you've ever trusted the Styles pane's "winning declaration" highlight while debugging a layered stylesheet. On the feature side, Web Inspector gains a visual CSS keyframe animation editor, continuing the same "see it instead of guessing it" direction Chrome DevTools took with its anchor-positioning editor a few weeks earlier.
CSS Grid has been broadly supported for years, which creates a false sense that "Grid just works the same everywhere." It mostly does, for the layouts tutorials show: a handful of fixed or fr-sized tracks and a few items. The bugs fixed in STP 255 live specifically in the intersection of Grid with percentage sizing and auto-fill — the exact combination production interfaces reach for once a grid has to adapt to unknown content length or an unknown number of items, like a card layout pulling from a CMS or a dashboard with a variable number of panels. Those are also the layouts least likely to get manually tested in Safari during development, because they "look fine" with placeholder content and only misbehave once real data with real aspect ratios lands in them.
auto-fill grids in Safari once this build reaches stable. If a card grid or dashboard panel layout has looked subtly "off" in Safari specifically — wrong row height, miscounted columns — this is the fix to watch for in the eventual stable release notes.cross-fade() for Safari. Any workaround built around Safari's non-conforming cross-fade() behavior can likely be removed once the fix ships to stable, since it now follows the same spec text Chromium and Firefox already implement.Safari Technology Preview is Apple's rolling preview channel, not a shipped Safari version — these fixes land in Safari proper (and WKWebView) on Apple's regular OS and Safari update cadence, historically a matter of weeks to a couple of months after a given STP build, not an immediate stable release. Teams that need the fixes sooner can install STP 255 alongside a regular Safari install on macOS Tahoe or macOS Golden Gate to verify behavior ahead of the public rollout, which is the usual purpose of the preview channel: catch regressions and confirm fixes before they reach every Safari and WKWebView user at once.