I'm pretty new to choosing compression libraries - I started with zlib and was delighted at how much faster and smaller zstd made things.

Since we kind of need a default "Need to compress something? Use this!" setting - would you prefer zlib over zstd, or something else for that role?

The only reason to pick anything but zstd is that platform support might be better.

If your platform/sdk/browser/standard-library comes with zlib/gzip/.. then it's often easier to just pick that.

No new dependencies is always a win. App size. Security, etc.

Otherwise, if zstd is easy to add, IMO I would always prefer, zstd, lz4 or brotli.

zstd or lz4