There are files with ZFS features for backward compatibility. Each file has a first line with a comment with OS version but many files have "Features supported by FreeBSD 11.3" even if the OS version in file name is different: # head -n1 /usr/share/zfs/compatibility.d/free* ==> /usr/share/zfs/compatibility.d/freebsd-11.0 <== # Features supported by FreeBSD 11.0 ==> /usr/share/zfs/compatibility.d/freebsd-11.1 <== # Features supported by FreeBSD 11.0 ==> /usr/share/zfs/compatibility.d/freebsd-11.2 <== # Features supported by FreeBSD 11.2 ==> /usr/share/zfs/compatibility.d/freebsd-11.3 <== # Features supported by FreeBSD 11.3 ==> /usr/share/zfs/compatibility.d/freebsd-11.4 <== # Features supported by FreeBSD 11.3 ==> /usr/share/zfs/compatibility.d/freebsd-12.0 <== # Features supported by FreeBSD 11.3 ==> /usr/share/zfs/compatibility.d/freebsd-12.1 <== # Features supported by FreeBSD 11.3 ==> /usr/share/zfs/compatibility.d/freebsd-12.2 <== # Features supported by FreeBSD 11.3 ==> /usr/share/zfs/compatibility.d/freenas-11.0 <== # Features supported by FreeBSD 11.0 ==> /usr/share/zfs/compatibility.d/freenas-11.1 <== # Features supported by FreeBSD 11.0 ==> /usr/share/zfs/compatibility.d/freenas-11.2 <== # Features supported by FreeBSD 11.2 ==> /usr/share/zfs/compatibility.d/freenas-11.3 <== # Features supported by FreeBSD 11.3 ==> /usr/share/zfs/compatibility.d/freenas-9.10.2 <== # Features supported by FreeNAS 9.10.2 Shouldn't the comment matches the file name?