> but I'm thinking of a project where more substantial additions have been made. The most famous example of that is AFAIK Firefox. There's a (perhaps outdated)

> but I'm thinking of a project where more substantial additions have been made. The most famous example of that is AFAIK Firefox. There's a (perhaps outdated) list at https://wiki.mozilla.org/Oxidation#Rust_Components https://wiki.mozilla.org/Oxidation#Rust_Components of places where Rust was used to replace some component in Firefox; the most famous of these are probably the CSS style calculation which came from the Servo project (https://hacks.mozilla.org/2017/08/inside-a-super-fast-css-engine-quantum-css-aka-stylo/ https://hacks.mozilla.org/2017/08/inside-a-super-fast-css-en...), and a renderer also from the Servo project (https://hacks.mozilla.org/2017/10/the-whole-web-at-maximum-fps-how-webrender-gets-rid-of-jank/ https://hacks.mozilla.org/2017/10/the-whole-web-at-maximum-f...).