If you are on an older build of Windows 10 (pre-1903), the high-resolution files are stored directly in your system files. Even on some newer builds, Microsoft occasionally leaves them in a specific subfolder. Open . Navigate to: C:\Windows\Web\4K\Wallpaper\Windows . Look for the file named img0_3840x2160.jpg . Downloading the Original Wallpaper
Since newer versions of Windows 10 only include the updated, lighter wallpaper, you can find the original 4K file on reputable archival or community sites: 3840x2160 How to Get the Old Windows 10 Default...
The Windows Wallpaper Wiki provides detailed history and often links to original file versions. If you are on an older build of
Sites like WallpapersWide host the "Hero" image in multiple aspect ratios and resolutions up to UHD. How to Apply the Wallpaper Once you have the file: How to Change Desktop Wallpaper in Windows 10 Navigate to: C:\Windows\Web\4K\Wallpaper\Windows