Safari 18.4 release brings major web platform enhancements

One week after its announcement on March 31, 2025, Safari 18.4 delivers substantial improvements to the WebKit engine powering Apple's browser across all platforms. The update focuses on compatibility, privacy, and developer experience while providing new tools for web applications.

According to the WebKit team announcement, Safari 18.4 introduces Declarative Web Push, a significant evolution in how websites can send notifications to users. This new approach, now available on iOS and iPadOS 18.4 for web apps added to the Home Screen, eliminates the need for a Service Worker when implementing push notifications.

The WebKit team explained the reasoning behind this approach: "Compared to the original Safari Push, which used a declarative model, requiring a Service Worker introduces added complexity for web developers. It also demands more from the system — consuming additional battery and CPU resources — and opens the door to potential misuse."

This development builds upon Safari's history with web notifications, which began in 2013 when Safari 7 on OS X 10.9 Mavericks introduced the capability to send push notifications across the web for the first time. The implementation of Web Push standards followed in Safari 16.1 on macOS and later expanded to web apps on iOS and iPadOS 16.4.

Extensive CSS improvements

Safari 18.4 delivers numerous CSS enhancements, with one of the most notable being the new shape() function. This addition addresses limitations in using clip-path for complex graphical effects, allowing developers to specify an SVG-style path with CSS units that respond to the element being clipped.

The update also significantly improves the functionality of details and summary elements with the new ::details-content pseudo-element. This enhancement allows for independently styling content that appears when details elements are opened and enables height animations without requiring JavaScript or additional containers.

For international typography, WebKit for Safari 18.4 adds support for text-autospace, which automatically introduces extra space to improve readability when transitioning between scripts, particularly beneficial for CJK (Chinese, Japanese, Korean) content mixed with Western characters.

Additional CSS improvements include support for sideways writing modes (sideways-rl and sideways-lr), gradients with only one stop, and fallbacks inside attr().

Enhanced HTML capabilities for developers

The update enhances the HTML color picker with support for alpha and colorspace attributes, allowing users to choose colors from the Display P3 colorspace and adjust opacity. These enhancements have been standardized in collaboration with the WHATWG community.

For iOS users, Safari 18.4 adds support for the webkitdirectory attribute on file input elements, enabling directory uploads through the document picker.

Web Inspector gets productivity boost

A significant productivity enhancement for developers is the addition of device viewport size presets in Responsive Design Mode, enabling quick testing of web page layouts. Presets can be rotated for portrait and landscape orientations, though the WebKit team notes these presets offer approximations rather than exact representations of device experiences.

The update also introduces application-specific automatic inspection and pausing of JSContexts, allowing developers to configure these options for individual apps rather than entire devices.

Media and WebRTC improvements enhance content creation

Safari 18.4 expands media capabilities with support for the Image Capture API, enabling the capture of images from cameras through MediaStream Image Capture API.

MediaRecorder has been enhanced to support WebM files using Opus audio codec with VP8 or VP9 for video, as well as ISOBMFF (fragmented MP4) files compatible with Media Source Extensions. High-quality, lossless audio tracks in ALAC or PCM formats are now supported, along with video tracks in H264, HEVC, and AV1 (for devices with AV1 hardware support).

WebRTC improvements include support for the MediaSession capture mute API and speaker selection API on macOS, allowing enumeration of speakers once microphone access is granted.

JavaScript and Web API advancements

JavaScript developers will benefit from several Iterator Helpers proposal implementations, enabling more efficient handling of large datasets through lazy data handling. The update also improves JSON parsing performance using SIMDe for fast scanning of strings.

New Web APIs include the Screen Wake Lock API for Home Screen Web Apps, preventing devices from dimming and locking screens – particularly useful for recipe applications or similar use cases. The dialog.requestClose() method for closing dialog elements and options to set invokers for popovers with showPopover() and togglePopover() methods have also been added.

The Cookie Store API provides asynchronous management of cookies and notifications about changes, though it exposes only name and value properties due to privacy considerations.

Security and privacy enhancements

Safari 18.4 removes the lock icon from the Smart Search field for HTTPS connections, acknowledging that secure connections have become the norm with more than 87% of all connections now made over HTTPS. The WebKit team noted that "the presence of the lock could be creating a false sense of trustworthiness, if users instead believe it's there to signal the website is trustworthy."

Users can now access connection security details through a menu option, which on macOS is found under Safari menu > Connection Security Details, and on iOS, iPadOS, and visionOS under Page menu > more > Connection Security Details.

In the EU, these details indicate connections made using an EU Qualified Web Authentication (QWAC) certificate, providing an indicator for enhanced trust and security.

WebKit continues focus on compatibility

Beyond new features, WebKit for Safari 18.4 resolves 184 issues across various categories, reflecting the team's focus on compatibility and quality. The update addresses issues in CSS, editing, JavaScript, media handling, rendering, and numerous other areas.

Browser-specific fixes include resolving an issue where sites would log out automatically after a brief time, addressing a significant user frustration point.

Availability across Apple platforms

Safari 18.4 is available on iOS 18.4, iPadOS 18.4, macOS Sequoia 15.4, macOS Sonoma, macOS Ventura, and visionOS 2.4. Users can update their iPhone, iPad, or Apple Vision Pro by going to Settings > General > Software Update. Mac users running Sonoma or Ventura can update Safari independently by going to System Settings > General > Software Update and clicking "More info..." under Updates Available.

Timeline of key Safari 18.4 developments:

• March 31, 2025: WebKit team announces Safari 18.4 with 84 new features
• April 2023-March 2025: Development of Declarative Web Push technology
• December 2024: Safari 18.2 added support for view-transition-name: auto
• April 2024: Original implementation of WebKit Web Push in Safari 16.1 on macOS
• 2017 (March): Unprefixed support for writing-mode properties
• 2016: Firefox implements Web Push standards
• 2015: Chrome implements Web Push standards
• 2013: Safari 7 on OS X 10.9 Mavericks introduces Safari Push
• 2011: Safari adds initial support for writing-mode (prefixed until March 2017)
• 2004 (April): Now-removed composite attribute added to img elements

The Safari 18.4 update represents significant progress in WebKit's capabilities, particularly for web applications and developers focused on cross-platform compatibility.