Go to Settings > Update & Security > Windows Update and click Check for updates . This is the only official way to get the latest DX12 files.
Searching for a "DirectX 12 offline installer download" will yield dozens of third-party websites offering custom installation packages. directx 12 offline installer
This installer does require internet. It copies legacy DirectX files into C:\Windows\System32 and SysWOW64 . Go to Settings > Update & Security >
If you are facing DirectX errors or think you are missing files, use these official methods: directx 12 offline installer
Overwriting core Windows system DLLs can cause permanent blue screen (BSOD) errors.
Launch dxsetup.exe from the extracted folder to install missing legacy components.