Edge 151 Replaces C++ XML Parser with Rust: No More Memory Bugs in DOMParser

The DOMParser API, XHR's responseXML, and SVG document parsing in Edge have all run through the same C++ XML parser for years, and that code has been a reliable source of memory-safety CVEs. Edge 151 replaces it with a Rust implementation. You get identical behavior and performance, but an entire class of memory-corruption bugs disappears at the language level. XSLT still uses the C++ path, so if your app does XSL transforms, you are not fully off the old parser yet. For everyone else, this is a transparent swap.

The CSS alpha() function lands alongside it: alpha(from red / 0.5) gives you semi-transparent red without recomputing color values manually. More importantly, shadowrootreferencetarget closes a gap web component developers have been working around for years: a <label for="checkbox-id"> outside a custom element can now reach an <input> inside its shadow DOM. No more JavaScript bridge code just to wire up form labels or aria attributes across the shadow boundary.

The release also adds soft-navigation and interaction-contentful-paint performance entries for SPA monitoring, plus WheelEvent.momentum to tell inertial scroll apart from direct user input. The Rust parser is the headline here: memory safety moving from the code reviewer's checklist into the compiler.