What causes a Steam demo incorrectly sharing the full game's app ID?

A Steam demo should have its own app ID; building the demo against the full game's ID makes ownership checks, achievements, and cloud saves bleed between the demo and the paid game.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix Steam Demo and Full Game Sharing One App ID

Quick answer: Create a separate demo app ID linked to the base game, build the demo to initialize with that ID, and gate content by build rather than by checking ownership of the full game.

If your demo unlocks paid content or shares saves with the full game, both builds are using the same app ID. Steam treats them as one product, so achievements and cloud data collide.

How to fix it

1. Use the demo app ID

Request a demo app ID in the Steamworks app admin and initialize the demo build with it via steam_appid.txt in dev and the linked launch in production.

2. Gate content by build

Limit demo content in the demo build itself rather than checking whether the player owns the full game; the demo should not even contain the gated assets where possible.

3. Separate saves and stats

Because the demo has its own app ID, its cloud saves, stats, and achievements stay isolated from the full game, avoiding cross-contamination at launch.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

Ship the fix, watch the signature disappear from the next build. That's how you know it's really gone.