Apple has released Safari 26.3 alongside today's system updates, bringing a mix of under-the-hood improvements and at least one major usability upgrade for Vision Pro users. The update introduces automatic dimming of surroundings when videos enter fullscreen on visionOS 26.3, helping users focus on content.

A significant technical addition is support for Zstandard (Zstd) compression, an open real-time algorithm developed by Meta. Apple says Zstd decompresses quickly enough to work on-the-fly, reducing device workload compared to Brotli which typically requires pre-compression during builds. The feature requires Safari 26.3 on iOS 26.3, iPadOS 26.3, visionOS 26.3, and macOS Tahoe 26.3.

For developers, the update adds an AbortSignal to Navigation API's NavigateEvent, providing a reliable way to cancel ongoing work when navigation gets interrupted. The WebKit engine also receives numerous bug fixes across CSS, DOM, media handling, rendering, and Safe Browsing. These include fixes for position-try boxes, anchor-positioned elements, HDR JPEG rendering, and timestamp handling. The comprehensive update demonstrates Apple's continued refinement of both user experience and developer tools in its web browser.