There currently is an issue where if game capture succeeds in capturing the game very soon after the game has only just been started up, it'll always capture the steam overlay. In other words a workaround to this is opening OBS after opening the game instead (for the time being). I'll see about making an option to wait until steam overlay is active before injecting game capture. It's definitely doable.
Osiris: My apologise.. 11 months old thread here: https://obsproject.com/forum/threads/game-capture-picking-up-steam-overlay.32317/
Any ETA for the new update?
fatmatrow: I've tried that work around.. It didn't work for me unfortunately.
0.14.1 this is still an issue.
As I mentioned in a prior post/edit:
Isolated the issue: When you uncheck Capture any fullscreen application it will capture the Steam Overlay regardless of settings. With the above setting checked, the issue does not happen. This can be a bit of a problem if you have other things fullscreen and you don't want to capture them.
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I'm able to reproduce this every time with a clean profile. The first run it will be fine but after that the problem occurs consistently.