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 practice of using watermarks to distinguish internal or debug versions likely originated during the development of the OS/2 1.1 Presentation Manager, early builds of which showed version information in the bottom left corner. Windows would later adopt the practice with Windows 3.0, with the first build known to display one being Windows 3.0 build 14, albeit in the bottom right corner, unlike OS/2. The watermark was later removed in the lead-up to the RTM, although they were soon 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.

Non-debug builds did not include any version watermarks until Windows 98 build 1351 and Windows 2000 build 1983 (the latter having the watermark hidden by default). Enabling Active Desktop would remove the watermark until it was disabled, as the Active Desktop page overlays the classic desktop including the watermark. Windows XP Starter Edition and Windows Vista Starter also feature a graphical watermark that overlays any visible windows.

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. In Windows 8, only the watermark appears when the copy was proven as non-genuine. 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 11065.

In earlier 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. Build 22000.51 and above has an additional watermark which may be automatically placed on the top right corner of the desktop when using the SE edition, stating that the machine is not set up securely and that potential data loss could occur. Furthermore, starting with builds 22557 and 22000.588, another watermark is shown on systems that don't meet the minimal system requirements.

Version
The most common kind of watermark identifies the operating system version and build and is displayed in the bottom right 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. However, potential security concerns such as running Windows in test mode or a Secure Boot misconfiguration may also cause this watermark to show together with a warning. 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, where it is not shown by default, by modifying or adding a registry entry:

Alternatively, the debug watermark, which also includes the Windows directory path, can be enabled on NT-based versions by setting the following registry entry:

Safe mode
In safe mode, Windows 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 debug editions of Windows NT before 2000) instead of the bottom right.