Disable Fullscreen Optimization Compatibility Shims

What it changes

Turns off Windows "Fullscreen optimizations" globally. Games that ask for exclusive fullscreen get true exclusive fullscreen, rather than a borderless window that Windows manages for them.

Why it helps

• Some older DirectX 9 and 11 engines stutter, hit unexpected frame caps, or show uneven frame pacing when the Desktop Window Manager stays involved.
• True exclusive fullscreen removes the compositor from the path entirely.

Trade-offs

• Modern games on Windows 11 generally run better with the optimizations on. The optimized path is the flip-model path that Auto HDR and windowed variable refresh rate depend on, so disabling it globally turns those off for fullscreen games.
• Alt-tab out of an exclusive fullscreen game is slower and may flash the screen.
• Disabling optimizations per game from the exe Properties, Compatibility tab is usually the better choice.
• Opt-in for these reasons: off by default and skipped by Apply Performance Preset.
• No restart and no administrator rights needed.

Details

• Sets GameDVR_FSEBehavior=2 and GameDVR_HonorUserFSEBehaviorMode=1 under HKEY_CURRENT_USER\System\GameConfigStore.

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Part of Performance Tweaks. This page is the same text as the app's Learn more button, generated from Help/tweaks/fse_behavior.md. To fix something, edit that file (or open an issue); wiki edits are overwritten on the next sync.