Depends on the game. Some have and GOG is supposed to provide keys for that.

I would assume they store one dummy key to ensure they do not run out of keys.

Offline installers have a generic key, yes.

We used to do wc3 multiplayer on our LAN with just one licence key. Diablo 2 as well. This is with original CD versions, two players for WC3 but on D2 we would add a Mac as well (our Mac wouldn't run WC3).

I never stumbled on a game that refused LAN play with same Keys.

AncapDude wrote on 2025-09-22, 00:17:

I never stumbled on a game that refused LAN play with same Keys.

I have, would have been once you went past 2 players and cant remember which game. Think it may of been C&C2/Ra2 or maybe Age of Empires or Empire Earth.
My "fix" was simply to find a keyen or at the very least a few random keys on the internet, as it's only for LAN play and not online, doesn't matter if its blacklisted.

But yes its entirely game specific.
Just as some games wont check the key but how many people had a CD, Blizzards' spawn method did this, with 1 in every 4 players needing a CD.

AFAIR, Quake 3 (maybe Quake 4?) needs different keys for every player.

Both GoG and Steam releases gives you keys for the game. I don't remember if the installer puts everything in place, or you have to manually put them (I remember that Quake 3 in Steam asks your for a key, but I can't tell about Q4).

BTW, there is no way to know which games have keys or not. I mean, you can get keys for your game (on GoG go to your game download page and click on More > Serial Keys; on Steam right click on your game > Manage > Product Keys) but there is no way to get a list of every game that needs/have a serial key.

Interesting. This is what Gemini spat out. Seems that Blizzard was not as strict as Westwood.

"Unlike Warcraft 3, the classic Command & Conquer games, including Red Alert 2, did not natively allow multiple players to play on a LAN with the same CD key. The game's multiplayer system was designed to prevent this, and if two players with the same key tried to join the same LAN game, one would be kicked with a "CD key already in use" error.

However, the Red Alert 2 community, being very active, developed workarounds for this problem. The CD key is stored in the Windows Registry, and players discovered that you could change the value of this registry key on different computers to make them appear to have unique keys."

So I took a different game out of curiosity:

"This is a classic question for older PC games. For Paraworld, the short answer is that you need a unique CD key for each player to play in a LAN multiplayer game.
While many older games allowed multiple players to connect on a LAN with a single key, this was not the case with all games, and Paraworld was one that required separate keys. The game's copy protection would prevent two players with the same CD key from joining the same session."

I will test this out to see if AI is right here.

I'm 99% sure (as it has been a very long time) that C&C2 and RA2, allowed 2 player LAN with the same key. It was one of the reasons games came on 2 CD's but no spawn install option. One for you, one for your friend.
Not sure about online games, Can imagine that was limited to individual keys and maybe what's confusing Gemini.

Main problem with the CD method was it didn't support the expansion packs, meaning you technically had to buy 2 copies if you wanted to play them in a network game.
Lucky these games were easy to no-cd which also meant your friends didn't return your CD's ruined (which happened to my copy of C&C Covert Op's)

Zup wrote on 2025-09-22, 04:47:

AFAIR, Quake 3 (maybe Quake 4?) needs different keys for every player.

The authentication only matters for online play. on lan it doesn't matter whether there's a key in or not (though quake4's ui will always want a key for any access)

From my own experience, whether you need a unique CD key for old LAN games really changes from title to title. I remember with things like Command & Conquer and some of the early Age of Empires games, you could sometimes get away with using the same disc and key for two people, but you’d run into trouble if you wanted to add more friends. Games like Quake 3 used to be stricter, especially when you tried to go online, but for LAN sometimes they didn't really check all that much.

Nowadays, when I look for older games to play with friends or just check how things work key wise, I usually check what’s required before buying. There’s a good site that helps with that cdkeyprices.ca, especially for comparing digital key prices and making sure I don’t end up buying the wrong version or a locked key for retro LANs. It’s useful if you need to check things like region or price for multiplayer games. Here’s one place you can look for cheap PC and console game codes.

Battle for Middle Earth II does need individual keys. Rise of the Witch King does too. So does Paraworld, Earth 2160 and some others.

SCSI "network": One SCSI bus, two computers. One CDROM drive is installed in 2 computers at the same time.

Disruptor wrote on 2025-10-08, 12:45:

SCSI "network": One SCSI bus, two computers. One CDROM drive is installed in 2 computers at the same time.

Media isn't the issue. Especially with virtual cd drives are common place.
It's once you load the software and it checks if the install key on PC1 is the same on PC2

I noticed the same thing when setting up a LAN a while ago. GOG basically skips CD key checks entirely. Most older games just need local network discovery to work, not key validation.

chinny22 wrote on 2025-10-08, 23:37:

Disruptor wrote on 2025-10-08, 12:45:

SCSI "network": One SCSI bus, two computers. One CDROM drive is installed in 2 computers at the same time.

Media isn't the issue. Especially with virtual cd drives are common place.
It's once you load the software and it checks if the install key on PC1 is the same on PC2

Ah. We overcome WarCraft II Spawn issue. It just was CD protection, no keys 😀