Rust 1.21.0 prerelease testing


Rust 1.21 is released on Thursday and builds are available now for testing. Release artifacts are uploaded to dev ( currently and will be promoted to prod ( this Thursday. The URL is

You can test rustup with

RUSTUP_DIST_SERVER= rustup update stable

Please let us know if you run into any issues! Pending any detected regressions these are likely to be the exact artifacts that we’ll release on Thursday.


As is traditional, I’ll leave a link to the release notes here:


Looks like those release notes are missing a bunch of stabilized libs: