Windows Fullscreen Optimizations Causing Input Lag

If your game has noticeable input lag or inconsistent frame pacing in 'fullscreen' mode, Windows might be secretly converting it to borderless windowed. Since Windows 10, Microsoft's 'fullscreen optimizations' intercept exclusive fullscreen and run the game through the Desktop Window Manager (DWM) compositor instead. This adds a frame or more of input lag. To check: while in a game, press Alt+Tab. If the transition is instant and smooth, you are in borderless windowed (not true fullscreen). True exclusive fullscreen has a noticeable screen flash and delay when Alt+Tabbing. To disable per game: right-click the game's .exe file > Properties > Compatibility tab > check 'Disable fullscreen optimizations'. Click Apply. For Steam games, right-click the game in your library > Manage > Browse local files to find the .exe. You can also set this globally via a registry key, but per-game is safer. Note that disabling fullscreen optimizations means you lose some borderless windowed benefits like instant Alt+Tab and better multi-monitor support. But you gain lower input latency and potentially better G-Sync/FreeSync behavior. Some modern games (especially DX12 titles) use a 'flip model' presentation that gives you the best of both worlds — for these games, fullscreen optimizations actually help. Test both ways and use what feels better for each specific game.