It's not clear to me that they are replacing it bit-by-bit.

https://4e6.github.io/firefox-lang-stats/

I don't have an over-time series, but if you're willing to take my memory at its word Rust's percentage has hovered at around 10% for a while now. It seems to have actually gone down recently. Combine that with efforts like Servo being wound down and their team being let go, and it makes me wonder what the future of Rust looks like in Firefox.

If anyone can shed some light on this I'd be interesting to know.

I think they stopped the rebuild. They were previously building a new browser engine called servo. Some of that work made it through to Firefox gecko. And then team was gutted.

This chart looks like it could use some filtering for what constitutes a language used to build Firefox. It seems questionable that HTML is used to build 16 % of it. I suspect that is a result of test cases being included in the chart as it is based off of the whole repo. I checked out the repository and it doesn't have the GitHub language bar I see on other repos, so I can't click the HTML bit in it to filter down the HTML files in the repo and see if they are mostly tests or not, but it is hard to imagine they would be anything else. Maybe bits of the browser Chrome but still, that wouldn't be a whole 16 % I think.

> Yes, but they are replacing it bit by bit - I mean, they even started Rust for exactly that purpose. So (without being a huge fan of Rust) the decision to start a "greenfield" browser project in a memory-unsafe language is questionable IMHO...

Maybe, but the speed with which SerenityOS, its programs and the browser has been implemented, with so few man-hours thrown at it kinda displays why C++ was chosen over Rust.

There is no comparable project in Rust that demonstrates just how quick you can go from "nothing" to Full-Fledged OS, with applications, with a browser.

Just from the Serenity project (if you've been following it), it looks like C++ is about 10x faster to write performant and safe code in than Rust.

> There is no comparable project in Rust that demonstrates just how quick you can go from "nothing" to Full-Fledged OS

https://www.redox-os.org/

>> > There is no comparable project in Rust that demonstrates just how quick you can go from "nothing" to Full-Fledged OS

> https://www.redox-os.org/

Doesn't that sort of prove my point?

I dunno if you've tried both SerenityOS and Redox - I have, and SerenityOS is just more complete and usable as a daily driver than Redox[1].

Redox developed over 7 years has less functionality than SerenityOS developed over 4 years.

[1] They both have a long way to go before being completely usable as a daily driver, but Redox has a longer way to go than SerenityOS.

Sort of... but that could be due to a host of other factors besides which language is better: how good the core developer(s) are at community-building, how committed they themselves are to the project... hell, even the fact that one project used GitHub (which reduces the friction for developers who are already on GitHub to start working on the project), while the other one has its own GitLab might be relevant.

I think it was more like "they were" up to the point the Rust team got layed off.