Safari Technology Preview 243: Enhanced Accessibility, Animation Fixes, and CSS Updates

Introduction

Safari Technology Preview 243 is now available for download, bringing a host of improvements and bug fixes to web developers and early adopters. This release is compatible with macOS Tahoe and macOS Sequoia. If you already have Safari Technology Preview installed, you can update it through System Settings under General → Software Update. This build includes WebKit changes between revisions 310600 and 312007.

Accessibility Improvements

Several issues affecting assistive technologies have been resolved in this release, making the web more inclusive for all users.

Context Menu in iframes

Fixed an issue where the contextmenu event was not triggered for elements inside iframes when activated via keyboard or assistive technology actions, such as VoiceOver’s VO+Shift+M. This ensures that context menus are now accessible across nested frames.

Color Picker Activation

Color picker inputs can now be properly activated using VoiceOver’s press action, resolving a barrier that prevented users from selecting colors.

ARIA Hidden Invalidation

Fixed invalidation of aria-hidden="true" when focus lands inside an aria-hidden subtree. This ensures that hidden content remains correctly obscured during navigation.

Base Select Element Support

VoiceOver support for base <select> elements has been improved, including the ability to close the popover on selection and correct positioning of accessibility paths when CSS transforms are applied.

Animation Fixes

Two key issues in CSS animations have been addressed to ensure smoother and more predictable motion.

Important Declarations and Animation Values

Previously, !important declarations did not override CSS animation values when transitions were also running on the same property. This has been fixed, giving importance specificity its intended precedence.

Transform Animation Correctness

Fixed an issue where identity matrix decomposition generated invalid quaternions, leading to incorrect transform animations. Animations now maintain accurate orientation.

CSS New Features

This release introduces two new CSS capabilities.

Contain: Style for Quote Counters

Added support for contain: style applying to CSS quote counters, as specified in CSS Containment Level 2. This allows developers to limit the scope of style recalculations.

Text-Autospace Insert Keyword

The insert keyword is now supported for the text-autospace property, offering more precise control over spacing in text layouts.

CSS Resolved Issues

Multiple layout and rendering bugs have been squashed to improve consistency across browsers.

Flex Layout

Fixed flex layout to use the used flex-basis instead of the specified value for definiteness evaluation. This aligns with the specification and prevents unexpected sizing.

Anonymous Block Positioning

An issue where element positioning was incorrect when the containing block was an anonymous block has been resolved.

Box Shadow on Table Row

box-shadow now works correctly on display: table-row elements.

Text Indent with Calc

Fixed text-indent with calc() containing percentages to correctly treat percentage components as zero for intrinsic size contributions, avoiding layout distortion.

Out-of-Flow Height

Out-of-flow content now has the correct height when set to fit-content.

Quirks Mode Flex Percentage

Fixed percentage size resolution in flex items when operating in quirks mode.

Clip-Path with Inset

clip-path: inset() border-radius values now render correctly at certain element and clip-path sizes.

WebKit Box Flexbox in Fieldset

Fixed -webkit-box flexbox emulation not sizing children correctly inside <fieldset> elements.

Performance for :where and :is

Improved performance on pages using :where and :is selectors, reducing style computation overhead.

Table Display with Border

Fixed an issue where elements with display: table could have incorrect layout when borders were present.

Aspect Ratio Rendering

Elements with border, position: absolute, and aspect-ratio: 1 now render as squares.

Conclusion

Safari Technology Preview 243 continues to refine WebKit’s implementation of web standards, addressing accessibility barriers, animation glitches, and CSS inconsistencies. Developers are encouraged to test their projects against this build and provide feedback to help shape the future of Safari.