Another commenter pointed out that Info-ZIP supports append, but alternatively it seems like tar is built for exactly this sort of thing. Instead of the usual g

Another commenter pointed out that Info-ZIP supports append, but alternatively it seems like tar is built for exactly this sort of thing. Instead of the usual gzipped tar archive (ie .tar.gz), just gzip (or something else) and then append the result to an existing tar archive. (https://www.gnu.org/software/tar/manual/html_node/appending-files.html https://www.gnu.org/software/tar/manual/html_node/appending-...) Also I'd preferably use zstd because it's a significant improvement in many ways and would afford you the option of placing a custom compression dictionary at the front of the tar archive.