Quick Answer

Full Screen Optimization (FSO) is a Windows feature that runs games in a borderless-window mode even when you select exclusive fullscreen. It causes issues including input lag, frame pacing problems, and broken NVIDIA Reflex. The fix is to disable FSO per-game via the executable's Properties menu or system-wide via a registry edit.

What Full Screen Optimization Is and Why It Causes Problems

Full Screen Optimization was introduced in Windows 10 to allow faster Alt-Tab switching by keeping games in a hybrid borderless-window state. While helpful for multitasking, it breaks several performance-critical features. When FSO is active, exclusive fullscreen mode is not actually enabled, which means NVIDIA Reflex latency reduction does not work at full effectiveness, G-Sync and FreeSync may not engage correctly, and the Windows Desktop Window Manager (DWM) compositor remains running, adding frame composition overhead. Competitive gamers running titles like Valorant, CS2, or Apex Legends on South African servers frequently report that disabling FSO drops their system latency by 5-15ms, which is significant at high framerates.

How to Disable Full Screen Optimization

The safest approach is per-game disabling rather than a system-wide change:

  1. Navigate to the game's main executable (.exe file) in File Explorer
  2. Right-click the .exe and select "Properties"
  3. Click the "Compatibility" tab
  4. Check the box labelled "Disable fullscreen optimizations"
  5. Click Apply and OK
  6. Relaunch the game

You can also right-click the game's desktop shortcut and access the same Compatibility tab. For games launched through Steam, right-click the game in your library, select "Properties," go to "Launch Options," and add -disable_d3d9ex (for older DX9 titles) or use the executable method described above.

For your gaming PC, also ensure you are running the latest NVIDIA or AMD drivers, as recent driver packages have improved how FSO interacts with Reflex and VRR.

Frequently Asked Questions

Will disabling Full Screen Optimization break anything? No. In the vast majority of cases, disabling FSO has no negative effects. Alt-Tab switching will be slightly slower (you may see a brief black screen), but in-game performance and latency will be equal or better.

Does disabling FSO affect all games or only the one I configure? Using the Compatibility tab method only affects the specific executable you configure. A system-wide registry edit would affect all games, but this is generally unnecessary.

How do I know if Full Screen Optimization is active? In-game, press Win + G to open the Xbox Game Bar. If the game is in "borderless window" mode despite you selecting fullscreen in its settings, FSO is likely active. NVIDIA's in-game overlay also shows the current display mode.

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