Tool and study coauthor here. The "more than 1 in 6" ratio is purely in the top 1000 most-downloaded crates on crates.io, which are the only ones we tested. I'

Tool and study coauthor here. The "more than 1 in 6" ratio is purely in the top 1000 most-downloaded crates on crates.io, which are the only ones we tested. I'm glad to hear of your positive experience with semver. Unfortunately, the issue with semver violations is that their impact has extremely high variance, easily ranging between "nobody noticed" and "ecosystem-wide pain": - Most of the semver violations we found appear to have never been reported or noticed. After talking to a representative subset of the maintainers of those crates, they were generally surprised to find out a semver violation had happened. - At the same time, a quick search for "violated semver" in Rust repos on GitHub will surface hundreds of issues, many of them heavily linked-to by issues in other projects. Every such issue represents dozens or hundreds of cumulative engineer-hours of triage and remediation in both the project where the semver accident happened and in affected downstream projects. All this work is regrettable, in the sense that both maintainers and downstream consumers would have preferred if it could have been avoided. Most semver violations aren't intentional -- they are accidents that happen to all of us regardless of skill level, carefulness, experience, etc. Most of the time, those accidents go unnoticed or have minimal impact. Every so often, they trigger nearly ecosystem-wide consequences for a few days or weeks. (Some examples on my blog: https://predr.ag/blog/toward-fearless-cargo-update/ https://predr.ag/blog/toward-fearless-cargo-update/ and https://predr.ag/tags/semver https://predr.ag/tags/semver ) And sometimes, breaking semver on purpose can be the correct thing to do! cargo-semver-checks aims to be a tool such that maintainers never have to say "if I had known this API change had happened, I wouldn't have published this version." Its biggest impact should be at minimizing or altogether preventing those ecosystem-wide semver issues that happen from time to time. Our day-to-day experience with semver should remain unchanged otherwise.