The website its absolutely great; the speed, long listings by page, intuitive and useful first page, the category pages turns all intuitive also, etc. So even unfinished its a great and really useful place, this are not just words, as a Rust newbie I had to comment it. Success.
By other side, when one visit crates_io, it is needed to employ a lot of time trying to figure out -besides I often get confused- if one crate, or one of the dependencies of its dependencies^n, require or makes use of a non Rust native code library (I mean non system related).
For me it is a very frustrating process, but I do it because in some cases can affect some long term decisions.
If some way it could be visualized the above in the listings, I think it would be really useful for all of us. A mere [Mix] flag or any visual in the listings would help a lot.
( a tiny box with [C], [CPP], [ADA], etc, would be better, but I guess that probably would require some code excessive analysis?, maybe would be an crate upload form mater).