The combined total of Rust, C, and C++ is only about half of the Firefox codebase. So it's more like 20% (of the code that it might theoretically replace). Be

The combined total of Rust, C, and C++ is only about half of the Firefox codebase. So it's more like 20% (of the code that it might theoretically replace). Because the code written in HTML and Javascript isn't going to be rewritten in Rust another language, probably ever.