Depends what you mean by "default". Windows ships with DirectX, OpenGL and Vulkan support. Call of Duty runs on Vulkan by default, for instance.

Vulkan is notable as being new (doesn't have legacy baggage OpenGL and DirectX have), is natively cross-platform, and is often more performant than other options for modern games.

Vulkan is not cross-platform if you include cross-GPU vendor, because it's too low level for that. You'd want to rewrite for different GPUs.

It's cross platform in that if you want, you can write implementations for other platforms. In addition to supporting multiple platforms in its current state.

> Windows ships with DirectX, OpenGL and Vulkan support.

Windows ships with DirectX. Your graphics card's software package can add support for other APIs.

Graphics API support is usually provided by drivers - and Windows ships with drivers that support Vulkan.

Graphics card drivers are also provided by the Graphics card vendor, not Microsoft.

That's true of DirectX as well though…

The difference is that Microsoft is responsible for the DirectX API on Windows but does not have anything to do with shipping OpenGl or Vulkan for Windows.

Microsoft plays roughly the same role a Khronos (specifies the API, provide conformance test suite, provide an SDK, etc.) but when it comes to actually “shipping” DirectX, Microsoft doesn't have anything to do either, it's all on the graphic card vendor to ship DirectX drivers. As an example, for a while after its release, many people didn't have access to DX12 at all, just because their GPU didn't have DX12 drivers.

So the situation is much less different between DirectX and Vulkan than you make it sound.

Linux and Steam Deck, ironically.

Though, for Windows it matters more what the GPU vendor wants you to use. Don't remember what that is atm.

Windows, Linux, SteamOS, Android, Switch

NVN is the native API on Switch.

Nintendo does support Vulkan as first class citizen on switch, and there high chance this is the reason of so many ports (besides units sold)