[jeffbee]

Does this mean the Zstd magic number is now cast in stone?

[cornstalks]

It's an Informational RFC, not a Standards Track RFC (https://en.wikipedia.org/wiki/Request_for_Comments#Status). That said, I think the magic number is pretty firmly established.

[lifthrasiir]

You may have mistaken Brotli (whose file format has no magic number and prevents an easy identification) with Zstandard (whose file format does have defined magic numbers 28 B5 2F FD or [50-5F] 2A 4D 18).

[jeffbee]

No I'm not confused, it's just that the Zstd magic number has had 8 different values over the years, so I'm just wondering if we're past that yet.

[lifthrasiir]

Ah sure. The wire format has been fixed since 0.8.0 (2016-08), so you must have seen a very early phase of development (which took one full year).

[stouset]

Can you shed some light on why this might be something of concern?

[wmf]

The file format was finalized years ago, so yes.