Mozilla have been developing a programming language called Rust for a while now. Two of the things it explicitly attempts to address are removing classes of potential memory bugs (like buffer overflows) and making it easier to write concurrent multicore programs. These two traits map nicely onto the browser landscape, as most devices have 2-8 cores now and memory bugs are a perennial problem.<p>To capitalise on this, and to give Rust a ‘halo’ project that uncovers potential issues early, Mozilla kicked off a project called Servo to research the ways that Rust could be used to produce a browser rendering engine. This has let them explore technologies like multicore rendering of a single page without dealing with the practical considerations (tried to find a nice way of putting it ) that Gecko has scattered throughout its codebase.<p>After Mozilla had made some progress Samsung became interested and started contributing a reasonable amount of code. I’m not sure if this is still happening, but you can see their interest given their prediliction for 8-core mobile CPUs.<p>Mozilla currently have no plans to replace Gecko with Servo outright, but they are folding Servo components back into Gecko when they’re portable and have obvious benefits. Gecko’s build chain can now handle Rust and I believe the URL parser is a port of Servo code (though I’m not sure it has landed yet). I think I recall a Mozilla engineer saying that Servo had progressed beyond a research project now, and it is pretty good at rendering reasonably complex sites, but they’ve still got a long way to go before it could be a drop-in replacement for Gecko.