Filippo ValsordaSep 9, 2025

TIL that you can compress .zip files with Zstandard (https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT compression method 93), and that libzip and 7-Zip support that.

https://libzip.org/news/release-1.8.0.html
https://github.com/ip7z/7zip/releases/tag/24.05

And Klaus Post's compress module has hooks, docs, and an example for how to produce and consume them with Go's archive/zip!

https://pkg.go.dev/github.com/klauspost/compress/zstd#readme-zstd-inside-zip-files

Show threadZT
@filippo Please stop trying to make that happen. zip files are only what legacy software can handle, so RFC 1951 deflate. Same way jpeg files with arithmetic coding instead of huffman are not going to happen. File formats from the 80s should not change. Create zst files. Create jxl files. Leave zip and jpeg alone.
Sep 9, 2025 at 2:32pmWeb
Show threadFilippo ValsordaSep 9, 2025

@ZTarantov zst is not an archive format. ZIP64 is a perfectly fine archive format with pluggable compression.

It's literally supported across C, Go, 7zz CLI, and 7-Zip Windows GUI.

Show threadZTSep 9, 2025
@filippo Does go standard library support zstd? Does Windows and MacOS built-in support it? https://pkg.go.dev/archive/zip
zip package - archive/zip - Go Packages

Package zip provides support for reading and writing ZIP archives.

Show threadFilippo ValsordaSep 9, 2025

@ZTarantov Go's third party support is linked in the top post.

Since I am compressing 1TB CT logs into 1000s of .zip files, I am comfortable ruling out that anyone will use the Windows or macOS built-in decompressers by double-clicking on each.