Quick answer: Verify your GOG build runs fully standalone and DRM-free without any launcher, then test any optional GOG Galaxy features like achievements and cloud saves both with and without Galaxy present. GOG DRM-free promise means the game must work offline and on its own, which is the central thing to QA.
GOG distinguishes itself with a DRM-free philosophy: games must run on their own, without a launcher or online check, and players can install and play them anywhere, offline, forever. GOG also offers GOG Galaxy, an optional launcher with features like achievements and cloud saves, but the key word is optional. QA for a GOG launch centers on verifying that your game truly works standalone and DRM-free, and that any Galaxy features you integrate work both with and without Galaxy present, which is the distinctive requirement of the platform.
DRM-free is the GOG promise
GOG core promise to players is DRM-free games: the game runs without any digital rights management, without requiring a launcher, without an online check, and without phoning home. Players can download the installer, install the game, and run it on any machine, offline, indefinitely. This promise is why players choose GOG, and your game must honor it, which is the central thing to verify in a GOG launch.
This makes the central QA task verifying true standalone, offline operation. Your game must launch and play fully without any launcher running, without a network connection, and without any GOG-specific software present. If your game secretly depends on a launcher or an online check, it violates the DRM-free promise and the platform expectation, so testing that the game runs completely on its own is the foundation of GOG QA.
Verify the standalone build runs offline
Test your GOG build the way a player will use it: install it from the actual GOG installer on a clean machine, disconnect from the network, and run it without GOG Galaxy or any launcher present. The game must launch and play fully in this standalone, offline state, since that is exactly the DRM-free scenario GOG promises and that many GOG players actually use.
Test that all features work offline, including any that might naively assume connectivity, and that saves work locally without any cloud dependency. A common bug is a game that assumes a launcher or online service is present and fails or hangs without it, which directly violates the GOG model. Verifying full offline, launcher-free operation on a clean machine is the most important single test for a GOG launch, because it confirms the DRM-free promise is kept.
Test optional Galaxy features both ways
If you integrate GOG Galaxy features, achievements, cloud saves, friends, multiplayer, the crucial requirement is that they are optional: the game must work with Galaxy present and providing those features, and equally must work without Galaxy at all, gracefully omitting the optional features. Test both states, because a Galaxy integration that breaks the game when Galaxy is absent violates the DRM-free promise.
Test that with Galaxy present, the features, achievements unlocking, cloud saves syncing, work correctly, and that without Galaxy, the game runs fine with those features simply unavailable, never crashing or hanging because Galaxy is missing. This with-and-without testing is the distinctive Galaxy QA requirement, ensuring the optional integration enhances the experience for Galaxy users without compromising the standalone, DRM-free experience for everyone else, which is the balance GOG requires.
Test the installer and updates
GOG distributes games through installers and offers updates, sometimes as standalone installers players run manually, since the DRM-free model means players can update without a mandatory launcher. Test that the installer works correctly on clean machines, installs to the right locations, and that the game runs after installation, since installer bugs block players before they even start.
Test the update mechanism you use, verifying that updates apply correctly and that, in keeping with the DRM-free model, players who update do not lose saves or break their installation. Because GOG players may update via standalone installers rather than a forced launcher update, test that path if you support it. A clean install-and-update experience is part of honoring the DRM-free, player-controlled philosophy that defines GOG.
A GOG launch checklist
Use this checklist for your GOG launch alongside normal game QA, centered on the DRM-free promise that is GOG defining feature. Add crash capture so any crash in the standalone or Galaxy-integrated build that reaches players is visible, including from offline players who reconnect later. The recurring theme is independence: the game must stand entirely on its own, and any launcher feature you add must be a genuine optional extra rather than a hidden dependency, so test the absence of Galaxy and the network as deliberately as you test their presence, because that absence is the exact scenario GOG players value and expect to work.
GOG launch QA checklist:
[ ] Game installs from the GOG installer on a clean machine
[ ] Game launches and plays fully without any launcher present
[ ] Game runs completely offline with no network connection
[ ] No hidden DRM, online check, or phone-home behavior
[ ] Saves work locally without any cloud dependency
[ ] Optional Galaxy features work when Galaxy is present
[ ] Game runs fine when Galaxy is absent, omitting optional features
[ ] Galaxy achievements and cloud saves work correctly if integrated
[ ] Installer puts files in correct locations and game runs after
[ ] Updates apply correctly without losing saves or breaking install
[ ] Crash capture covers standalone and Galaxy builds
[ ] Game never hangs or crashes due to missing Galaxy or network