Everything indicates that Galaxy is required for cross-play with Steam. Non-Galaxy copies can still have online multiplayer via Direct IP.

What the hell is a non-galaxy copy?

Direct IP works fine across all systems and platforms, last I tried. Galaxy & Steam are optional.

The ones that can be downloaded from the library via the browser and can be played without Galaxy.

Thanks for the information.

Added to the lists.

Redout Solar Challenge Edition has a splitscreen multiplayer.

Fight'N Rage has local multiplayer (on a single PC).

More games:

Games that can be played in multi player mode on a single PC via hotseat, splitscreen etc...
Hot seat:
Epic Pinball: The Complete Collection (up to 4P).
Pinball Gold Pack (up to 8P).
Co-op (same screen):
Cuphead (2P).
Metal Slug (2P).
Metal Slug 2 (2P).
Metal Slug 3 (2P).
Metal Slug X (2P).
Rayman Origins (up to 4P).

Thanks, added to the list.
Adding the numbers of potential players is a good idea.
It may be possible that I soon reach the character limit in the first post, I may have to make an additional later one and link there or to some outsourced spreadsheet soon.
Does anyone here have practice with setting up a spread sheet?
It would probably be nice to have the names only once in the list on the left and then additional rows for "Galaxy only", "LAN enabled", "Hot seat" and "Split screen" beside it.

Mortal Kombat 4 has been released and it falls in the "Games that can be played in multi player mode on a single PC via hotseat, splitscreen etc" category.

Nice and informative thread :)

I really hope we can get more multiplayer stuff on gog.

Wait, why is galaxy required for crossplay? If the game's patched for true DRM free spec, then you should be able to crossplay without any sort of client required....unless I'm missing something....

I can't remember if I've seen this posted somewhere or if i posted it somewhere, but GoG is now only doing single player drm free spec and not the full game, of which includes the multiplayer/coop aspect if there is one, right?

Now that the thread is bumped:
* Konami Collector's Series: Castlevania & Contra: As per the product page, "Note: Contra and Super C support local multiplayer."
* Serious Sam 4 has co-op, but I don't know the exact details.
* Silverfall: Complete: As per the product page, "NOTE: Multiplayer mode is only available via LAN connection."
* Battle Engine Aquila: As per the product page, "Note: Local multiplayer is supported."
* Summer & Winter: Olympic Challenge has multiplayer, but I don't know the exact details.

For the record, I don't own any of these games.

Read this post. Sorry for the confusion.

IIRC correctly, some devs said that "crossplay" between Steam and Galaxy means that the Steam version actually uses Galaxy infrastructure for multiplayer instead of the Steam, hence why it's something that needs to be added since day one and cannot be added later.


Correct

No Man's Sky mentions this in the store page:

Please note: The GOG Galaxy Client is required to access online features for No Man's Sky.
The game features online components introduced in updates (SYNTHESIS, BYTEBEAT, LIVING SHIP, EXO MECH, CROSSPLAY, DESOLATION and ORIGINS) that require Internet connection.

Would it count for this thread?

Streets of Rage 4 had a recent update and the following text was added to the store page:

Please note: The GOG GALAXY Client is required to access online features. Multiplayer is available only between GOG.com users.

According to someone in the most recent post on Street of Rage 4's forum, it's indeed a Galaxy-exclusive multiplayer that was added