[mappu]

Precomp works by brute-forcing the zlib/.../ parameters used to get byte-identical input; then decompressing; and (optionally) recompressing with a stronger compressor.

It was closed-source for a long time and AntiX was an open source version.

One interesting use case is for archiving Android ROMs for projects such as LineageOS. Each ROM is a zip file, they differ in bytes almost entirely and storing a long amount of history takes a lot of space. But under precomp, the differences between two nightly builds are quite small, and they can be packed together into a solid archive for a significant (90%+) space saving.