Watermark

A watermark is a text label shown on the Windows desktop that overlays the desktop wallpaper. Watermarks are used to identify the operating system version as well as report system errors or inform the users of internal builds about company policy.

History
The first Windows build known to display a kind of watermark is Windows 3.0 Debug Release 1.14; it was later removed in the lead up to the RTM. Watermarks were reintroduced during the development of Windows 3.1 as seen in the SDK debug kernel which, if applied on top of an existing copy of Windows, displays a shaded label in the bottom right corner identifying the current operating mode and the Windows version. The details of the current operating mode were removed during Windows 95 development, as they became redundant with the removal of Standard mode and 286 support.

Watermarks did not appear on non-debug builds until Windows 98 build 1351 and Windows 2000 build 1989.1. Enabling Active Desktop would remove the watermark until it was disabled, as the Active Desktop page overlays the classic desktop including the watermark.

Watermarks can sometimes include legal notices or warnings. If a copy of Windows Vista or Windows 7 is not activated, a watermark with "This copy of Windows is not genuine" message will appear in addition to turning the desktop background black. Starting with Windows 8 build 7788, internal builds display a separate message stating that the software is Microsoft confidential material, in addition to warning users about the legal consequences of sharing these builds outside of Microsoft; the same warnings were also shown in. The last known build to contain this warning message is Windows 10 build 14389.

In internal Windows 11 builds such as build 21990 a message is displayed on the bottom right corner which reminds the user to not take any screenshots of the build. In Windows 11 build 22000.51 and above, an additional watermark may be automatically placed on the top right corner of the desktop if the current SKU is SE, stating that the machine is not set up securely and that potential data loss could occur.

Version
The most common kind of watermark identifies the operating system version and build and is displayed in the bottom left corner. It is most commonly associated with pre-release versions, where it is enabled by default with no option to disable it unless one modifies the system files. Debug builds will also display the path to the currently loaded Windows installation below the version information.

It is possible to enable the watermark on release builds, which don't show it by default by modifying or adding a registry entry:

Using the operating system in test mode or Secure Boot errors may also cause this watermark to show together with an informing message.

Safe mode
When starting Windows in safe mode, the OS displays watermarks in every corner saying "Safe Mode". Additionally on NT-based versions, the build number is displayed on the top of the desktop (similar to the debug compiles of Windows NT before 2000) instead of the bottom right.