Qt (/ˈkjuːt/ or /ˈkjuː ˈtiː/; pronounced "cute"[7][8] or as an initialism) is a cross-platform application development framework for creating graphical user interfaces as well as cross-platform applications that run on various software and hardware platforms such as Linux, Windows, macOS, Android or embedded systems with little or no change in the underlying codebase while still being a native application with native capabilities and speed.

With Qt Quick, rapid application development for mobile devices became possible, while logic can still be written with native code as well to achieve the best possible performance.

Additionally the KDE project provides unofficial support for, at least, Qt 5.15, i.e. not just for commercial users.

In 2017, the Qt Company estimated a community of about 1 million developers worldwide[18] in over 70 industries.

[97] The Community version is under the open source licenses, while the Indie Mobile, Professional and Enterprise versions, which contain additional functionality and libraries, e.g. Enterprise Controls[97] are commercially sold by The Qt Company.

In addition to Qt Creator, Qt provides qmake, a cross-platform build script generation tool that automates the generation of Makefiles for development projects across different platforms.

In the summer of 1990, Haavard Nord and Eirik Chambe-Eng (the original developers of Qt and the CEO and President, respectively, of Trolltech) were working together on a database application for ultrasound images written in C++ and running on Mac OS, Unix, and Microsoft Windows.

[1][118] They began development of "Qt" in 1991, three years before the company was incorporated as Quasar Technologies, then changed the name to Troll Tech and then to Trolltech.

As it was based on Qt, many people in the free software movement worried that an essential piece of one of their major operating systems would be proprietary.

At the end of 2001, Trolltech released Qt 3.0, which added support for Mac OS X (now known as macOS).

In 2002, members of the KDE on Cygwin project began porting the GPL licensed Qt/X11 code base to Windows.

[126] This was in response to Trolltech's refusal to license Qt/Windows under the GPL on the grounds that Windows was not a free/open source software platform.

This was resolved when Trolltech released Qt 4.0 also for Windows under the GPL in June 2005.

[134] One month later, Nokia announced the sale of Qt's commercial licensing and professional services to Digia, with the immediate goal of taking Qt support to Android, iOS and Windows 8 platforms, and to continue focusing on desktop and embedded development, although Nokia was to remain the main development force behind the framework at that time.

The traditional C++-only QWidgets continued to be supported, but did not benefit from the performance improvements available through the new architecture.

[140] Qt 5 brings significant improvements to the speed and ease of developing user interfaces.