Summary

Safari 27.0 adds a local Safari MCP server that lets coding agents inspect and test web pages, alongside new HTML, CSS, WebAssembly and debugging capabilities. WebKit also reports 844 fixes in the release.

WebKit’s Safari 27.0 feature overview highlights a new Safari MCP server for coding agents, customizable HTML form controls, scroll anchoring, broader 3D support and extensive standards work. The release overview, published on September 17, 2026, lists 83 features compared with 58 in the first beta and reports 844 fixes, up from the 525 fixes announced at WWDC.

Contents

Safari MCP connects coding agents to a local browser

Safari 27.0 includes a Safari MCP server that allows a coding agent to work with a Safari browser window while developing a website. WebKit says the server can provide the agent with access to the page’s DOM, network requests, screenshots and console output.

That gives an agent the ability to inspect how code renders in Safari, verify states in forms and checkout flows, compare computed styles and layout with other browsers, check for accessibility problems such as missing labels or poor contrast, and examine navigation timing and resource-load times.

The server runs entirely on the developer’s local machine and makes no network calls of its own, according to WebKit. It does not access personal information in Safari, and captured data is sent directly to the agent being used rather than to Apple.

Developers must first enable Safari > Settings > Developer > Allow remote automation and external agents. WebKit provides setup commands for Claude Code and Codex using /usr/bin/safaridriver --mcp, as well as a configuration format for other agents.

New HTML, CSS and 3D capabilities

Safari 27.0 adds Customizable Select, which allows the native HTML <select> control to be restyled with CSS instead of replacing it with JavaScript and collections of generic elements. Developers can enable the new behavior with appearance: base-select. The control retains browser support for keyboard navigation, screen readers, form submission, validation and change events.

New pseudo-elements including ::picker-icon and ::checkmark expose parts of the control for styling. Developers can also place HTML elements inside an <option> and use <selectedcontent> to control how the selected item is displayed. Safari’s new default styles include support for light and dark modes, forced colors, disabled states and touch-friendly spacing.

Scroll anchoring is another user-facing change. When content such as an image, advertisement or comment is inserted above the position being viewed, Safari can adjust the scroll position to keep that content in place rather than making the page jump. The behavior is enabled by default through overflow-anchor: auto, with overflow-anchor: none available when a site needs to opt out.

The HTML <model> element, which first appeared in visionOS, is now available in Safari on iOS, iPadOS and macOS. It embeds 3D models in a page and can use multiple sources with an image fallback. Safari 27.0 also adds an Immersive API for websites on visionOS, allowing a site to provide an immersive environment through a <model> element and a JavaScript call.

Other platform additions include the auto value for responsive-image sizes, support for WebAssembly JavaScript Promise Integration, service-worker static routing, improvements to ReadableStream, and support for additional WebGPU, WebRTC and WebCodecs capabilities. WebAssembly JSPI allows synchronous-looking WebAssembly code to suspend while waiting for JavaScript Promises, which can simplify the porting of programs that expect synchronous input and output.

A larger focus on compatibility and developer tooling

WebKit describes Safari 27.0 as a quality-focused release as well as a feature release. Its reported fixes cover compatibility with specific websites and languages, rebuilt or expanded implementations, standards alignment and interactions between features that already worked individually.

The release includes an all-new ECMAScript module loader implemented in native C++. WebKit says the rewrite addresses module execution ordering and initialization issues, including problems involving top-level await, and was validated against test262, the Web Platform Tests and additional test cases.

Safari 27.0 also brings several Web Inspector improvements. The color picker displays contrast information while colors are edited, the Network tab shows every request in a redirect chain, and the Elements and Timeline tabs provide more information about grid layouts, layout roots and rendering events.

For native developers using WKWebView, the release adds APIs including WKJSHandle for using JavaScript object references from native code, controls for configuring content worlds, form-submission notifications, DOM-node snapshots between web views and more targeted cookie retrieval.

One standards-related feature is explicitly still evolving: WebKit identifies the BigInt Math proposal as TC39 Stage 1. Safari 27.0 adds functions such as BigInt.sqrt(), BigInt.cbrt(), BigInt.min() and BigInt.max(), but the source notes that the exact API may change as the proposal progresses.

Sources