Steam – What does it mean when a Steam download says Preallocating

I'm guessing:

1. Verifying the game is legit (DRM).
2. Verifying the game is up-to-date.
3. Verifying the requirements for the game (e.g. directx) are still met.

Although (3) should theoretically only be checked on the first run, I'm pretty sure it's actually checked on every run - I saw a few games that always show a brief "installing directx" line even after the first run. Maybe it is done to verify no hardware or software changes were made to the system that can break the game.

This is just a guess, though... if you want to know for sure, I suppose you can monitor the Steam process at the moment it is launched (e.g. with a network analyzer and some process monitor such as sysinternals).

I believe the ? means that Steam isn't sure if it's synced with the Steam Cloud. When you launch the game, or if you toggle cloud support for a game, the icon turns from the "question mark" to just a cloud icon. I tested this with a couple of games in my library, and this seemed to be a pattern. I can't find any Steam FAQs on this topic, so this is more of an educated guess backed up by some research.

I presume that on launch, Steam checks in with the cloud servers to see if there's any updated information to sync, and then it "knows" that the data is properly synchronized. At other times, it's possible that it has changed since the last time Steam checked, so it shows the question mark.