* Testing
** GeckoDriver, a WebDriver implementation for Firefox integrated via marionette protocol: {{bug|1340637}} ([https://github.com/mozilla/geckodriver/releases standalone releases])
** [https://github.com/mozilla/grcov grcov], a tool to collect and aggregate code coverage data for multiple source files, used in Firefox CI.
* Build system, etc.
** [https://github.com/mozilla/sccache/ sccache], compiler cache with s3 storage. Caching C++ and Rust compilation, used in Firefox CI.