A web desktop or webtop is a desktop environment embedded in a web browser or similar client application. A webtop integrates web applications, web services, client–server applications, application servers, and applications on the local client into a desktop environment using the desktop metaphor. Web desktops provide an environment similar to that of Windows, Mac, or a graphical user interface on Unix and Linux systems. It is a virtual desktop running in a web browser. In a webtop the applications, data, files, configuration, settings, and access privileges reside remotely over the network. Much of the computing takes place remotely. The browser is primarily used for display and input purposes.

The terms "web desktop" and "webtop" are distinct from web operating system, a network operating system such as TinyOS or distributed operating system such as Inferno. In popular use, web desktops are sometimes referred to incorrectly as web operating systems or simply WebOS.

In the context of a web desktop, the term Webtop was first introduced by the Santa Cruz Operation (SCO) in 1994 for a web-based interface to their Unix operating system. This application was based on the provisional application entitled "The Adaptive Internet Protocol System" filed 13 November 1997, serial number 60/065,521 and is the U.S. patent for the technology used in the Tarantella Webtop. Andy Bovingdon and Ronald Joe Record, who both explored the concepts in different directions, are often credited as the inventors. The initial SCO Webtop, developed by Record, utilized a Netscape Navigator plugin to display applications in a browser window via TightVNC. A trademark application for SCO Webtop was filed with the U.S. Patent and Trademark Office on November 8, 1996. To avoid confusion with the more complex technology incorporated into the Tarantella Webtop SCO abandoned it on 24 December 1997.

Bovingdon's three tiered architecture (TTA) concept was launched as the Tarantella Webtop. This technology originated from early commercial use of web server technology by SCO. the first OS vendor to include a commercial web server, NCSA HTTPd, and commercial web browser, NCSA Mosaic. Their X.desktop product line, obtained when they acquired IXI Limited in the UK, was the first to have icons for URLs (controlled via the Deskshell scripting language) and an HTML-based help system, named DeskHelp, which extended the NCSA Mosaic web browser to include APIs and scripting linked to the X.desktop product for interactive control. The IXI Limited scripting language based on Python was later replaced with JavaScript. Tarantella allowed real Unix and Windows applications to be displayed within a web browser through the use of Java to form a true web based desktop or Webtop.

The first SCO Webtop releases were part of SCO Skunkware before being integrated into SCO OpenServer version 5 and UnixWare 7. Tarantella was subsequently purchased by Sun Microsystems and integrated into their Sun Secure Global Desktop.

Byte magazine referred to the Webtop as a network user interface (NUI).

In June 2011, Google released an operating system for web connection named ChromeOS and several 11-12" netbooks from Acer and Samsung have implemented the system. It made up a useful fraction (~10%) of 2012 netbook sales.

The following tables compare general and technical information for several web desktops.