How to check DOOM version?

I need to update my copy of DOOM II so I can play it online through ZDaemon, because I am getting that usuall error message about how my WAD is incompatible.

How can I check what version of DOOM II I have?

When the game is loading in DOS (before the intro screen), the version number is on that bar at the very top.

Once you figure out your version, you can get the patches here or here.

If you have the censored German version of Doom II (it lacks levels 31 and 32) or the 1.666 pirate copy, those patches may not work correctly.

By exclusion, based on bugs ;-)