A succinct, good answer. I knew about the "exclusive" access, but none of its downsides.

Also borderless fullscreen can allow the game to render at a lower resolution but scale the graphics up using the GPU rather than change the screen's resolution. This is useful when a display has issues at some resolutions or simply cannot handle that video resolution at all. I have seen some tablet PCs drivers that can only handle 2 or 3 resolutions other than native, none of which scale properly. Where games did a better job of scaling than the drivers.

Borderless Fullscreen alss plays a /lot/ nicer with multiple monitor setups than normal fullscreen, while letting you use all the pixels on one monitor for a game.

With Windows 7, and further improvements in Windows 8, the internals have changed so there is no longer as much latency when using borderless windowed. Therefore there isn't any advantage to using real fullscreen any-more. Considering the issues with multi monitor, alt-tab and notifications, it simply isn't worth it.

Does this reason apply to mobile environments too?

I'd like to add one more point regarding multiple displays. 'borderless fullscreen' allows you to click on another display without minimizing itself to the taskbar, so you can actually play the game while doing other things on another monitor.

@Programmdude Well, there is still an advantage when you need something special - like a different colour palette or such. But yeah, it usually isn't worth it - emulating everything on the GPU is just so cheap there's hardly a point, and in the kind of games where you want to use such effects, you usually have a lot of GPU power left over :)

Bless CDProjectRed for their borderless Witcher 3.

@StephaneHockenhull: There's no reason why you can't do the upscaling in-game fullscreen.

"...which means a lot more work in handling resolution switching, resource management and so on...". Why is this the case? I'd think that a game having exclusive control over the GPU would make things easier for the game.

Don't forget the music. A borderless window doesn't overtake the audio output. Basically you are able to listen to music with your "insert music player app" while playing. If you go fullscreen, the only audio processed is the one of the game.

@Chro The game needs to do all the book-keeping. There's a lot of book-keeping to do, and most programmers only know about a fraction. Better keep those complicated situations to the OS programmers who already solved them :) Example - when you have exclusive access to the GPU and you load the texture, losing that exclusive access (e.g. Alt+Tab) also loses the texture. There's no way around it - you explicitly said that you don't want to coöperate - that's what exclusive means. And if your game accesses the GPU in the background, you crash. On restore, you need to restore the full GPU state.

@OddDev Actually, that's separate. You can have coöperative audio access, while you have exclusive video access. The basic arguments are the same for audio and video, though - exclusive is (more or less) faster, coöperative plays nice. Exclusive made a lot more sense when you simply didn't have the resources to run both the game and other applications at the same time - but now, when I can play on one screen while playing HD video on another, it's a heavy burden with little pay-off.

I'm interested to know how the Steam overlay fits into this. Is it just as bad as alt-tab or does it being an overlay make it better?

@Luaan Ok thanks. Explains why there's usually a bit of a black screen as soon as you switch back to the fullscreen game - I guess it has to reload some resources. So when a game doesn't have Alt+Tab that's because the developers didn't program it in, rather than that they specifically disabled it?

@Chro It basically has to reload all the resources that were loaded to any exclusive context. You can make this faster by keeping the resources in RAM as well as VRAM instead of reloading from HDD, but that isn't exactly cheap. Alt+Tab "works" by default (it's handled by the system, not the application - note how it still works if the app stops responding), but if you don't handle it properly in an exclusive application, you crash - and handling it properly is a lot harder than forbidding Alt+Tab :) In Windows 9x, you could (and did) even disable Ctrl+Alt+Del this way for extra malice.

@Programmdude Freesync only worked in exclusive full screen mode until december 2016 (Crimson ReLive 16.12.1 added support for borderless fullscreen), which was a pretty big advantage. [Pity it still doesn't support normal windowed mode]

I don't know how relevant this is but; Whenever I stream or try to record my screen with certain software, no matter how much fiddling I do with the recording setting, it does not pick up the fullscreened game (not borderless/FS). Similar on Skype-screensharing and Teamviewer type clients.

The full screen vs. borderless window can be significant. When I used to play World of Warcraft on an older computer, it would take 5-10 seconds to alt-tab out of full screen, but only take a fraction of a second when using the borderless window selection. The performance of borderless was only slightly less than full screen exclusive mode, perhaps a few fps, but the ability to alt-tab more than made up for it.