Reproducible Builds
A set of practices for making a build produce a bit-for-bit identical artifact every time from the same source.
The reason it matters is supply chain: if the binary you ship cannot be reproduced from the source you published, nobody - including you - can verify that the two correspond. Reproducibility turns “trust the build server” into something checkable by anyone.
The things that break it are mundane and everywhere: embedded timestamps, absolute paths, locale, filesystem ordering, and anything that hashes a map iterated in random order. The site catalogues each one and how to fix it.
See also: