I can't do that because even when I look now, I say "oh.. when did I buy that game?" Those numbers were always same for me.

I am thinking about that Excel file. Is there an easy way to copy paste the list? For some reason, GOG page does not allow me to copy paste neither in list nor in GRID view.

I do not play games so I probably only downloaded 50 games at most. I am just collect games.

It looks like Hotline Miami is one of the 600.

Nope. My Hidden section is 0 (Zero).

Thanks everyone for the suggestions.

At least I can copy from GOG list view, I'm using Opera.
Note that you may need to click outside the list to be able to select them all, like somewhere left from the first thumbnail picture.

Then in Excel paste as text-only, then format a bit, and there you have it.

How about the comic book? If you got that, it should be its own product, not an extra/DLC to the game. If you didn't get it, of course you wouldn't have it.

Ok so I ran gogrepoc.py for my GOG game collection (1650 games at the moment), in order to see if something has been dropped from my GOG library recently. The previous time I ran gogrepoc was 5th of Dec, so I could detect changes between that and last night, regarding those 1650 games that I have.

I noticed one anomaly: gogrepoc had "cleaned away" a directory called "copy4". It contains no game or extras files, and its !info text file says this:

-- Game overlay --

title.......... copy4
game id........ 1430742867
url............ https://www.gog.com/game/the_witcher_3_wild_hunt_free_dlc_program

game items.....:

Not sure if that has been shown as an extra "game" in people's libraries, and now GOG removed it as obsolete? Something related to the TW3 "free DLC program", I don't recall if it was shown as a separate item in the library before. It is odd though that the directory is named as "copy4", usually that directory is named after the game's title (e.g. "the_witcher_3_wild_hunt_game").

Other than that, I didn't detect any actual games going missing or two titles being merged into one, but then it is not like I own ALL the GOG games. Only measly 1650 of them (the newer the game is, the less likely I have it as I am a smart shopper waiting for sales and games having received all DLCs and updates; plus I tend to shun away from certain kind of indie games having retro "pixel-art" graphics and SID-like music, unless they are sold dirt cheap or get like massively positive reviews, like The Shovel Knight).

Engerek, if you want to confirm whether I have all the same games as you (which would confirm whether or not this is the only recent anomaly for you as well), you can provide me your game list in e.g. private message, I'll do a quick cross-check if I have all the same games. EDIT 2: On the other hand, if the removed game would be some that I never had in the first place, I guess I couldn't detect it anyway, so maybe this is not so useful after all... :)

EDIT: Of course it is also possible that GOG has removed some game from your account only (and not from others, like me), for reasons unknown. You haven't been buying or trading GOG game keys from G2A and such shady places with hookers, booze and card games?

Out of curiosity, do you back it all up? I have started a windows only/english only backup and it say about 2.5 or so TB. At this rate my two 10 TB discs in raid1 will get full quite quickly.

Yes, now it is all (again) backed up, as I just ran gogrepo. English Windows versions only. Now it is 3.03 TB in size, backed up onto a single "5 TB" (= 4.3 TB in real life) 2.5" USB hard drive.

A single local backup will do for now as it doesn't seem imminent GOG would be closing down, so for now I have my secondary backups on GOG servers. I'll consider mirrored local backups if and when it seems more probable GOG would be going offline (which is how I have backed up e.g. my DotEmu games, since I can't download them from DotEmu anymore). :)

A proper RAID setup would be nice, maybe I will consider it at some point.

I went with raid1 because I wanted to back up lots of personal stuff also. Under 3TB. Still, I was amazed how large the footprint of my library is (i have about 10% fewer games than you). I guess when space gets near 80% I will expand the storage with 2 more hdds. By then I hope they get cheaper.
Btw 10TB discs are just 9TB in fact :(.

I also have 1 less game on my library, i just noticed it today.

I have TW3, so that could be but the "free DLC program" always was inside my copy of TW3, never as a separate item on the library. I don't know if, despite that, GOG counted it as if it was antoher game.

Anyway, 1 less game in my library and too many games to check everyone right now, i'll need to go through all my external backup disks to find what is missing unless someone can confirm first that it were the free dlcs for TW3.

Not quite...
https://www.unitjuggler.com/convert-memory-from-TB-to-GiB.html?val=10
https://www.unitjuggler.com/convert-memory-from-TB-to-GB.html?val=10

If I am understanding that info file correctly, possibly the phantom title in the library wouldn't have been shown as TW3 DLC, but either with an empty name or with a title "copy3". The URL revealed it was somehow related to TW3 DLCs (which, like you said, are offered within the original TW3 item anyway).

I haven't kept exact count of my games so I don't know if I also had one more "game" before, but if I did, I am certain that is the culprit, as I didn't detect any other titles going missing (since Dec 5th).

Actually it's 9.09 TiB https://www.unitjuggler.com/convert-memory-from-TB-to-TiB.html?val=10
Anyway it's a stupid ripoff scheme of the HDD industry.

During the last sale they added in the library a fake game without picture and description, which precisely linked to the pack of free DLC of Witcher 3. With a purchase or a refresh of the profile it disappeared and with it the count of games dropped by one. Perhaps it is the same problem.

I received a reply from support. It seems they've been doing some cleanup recently.

People who were subscribed to the ancient Galaxy Beta before it became publicly available had the Beta as a game card in their library. It has been automatically hidden since quite a while ago and was recently removed which also caused the game count to go down by one for people who had the beta.