Original author(s)John Ousterhout
Developer(s)Tcl Core Team[1]
Initial release1991; 33 years ago (1991)
Stable release
8.6.13[2] Edit this on Wikidata / 22 November 2022
Written inC
Operating systemCross-platform
TypeWidget toolkit

Tk is a cross-platform widget toolkit that provides a library of basic elements of GUI widgets for building a graphical user interface (GUI) in many programming languages. It is free and open-source software released under a BSD-style software license.

Tk provides many widgets commonly needed to develop desktop applications, such as button, menu, canvas, text, frame, label, etc. Tk has been ported to run on most flavors of Linux, macOS, Unix, and Microsoft Windows. Like Tcl, Tk supports Unicode within the Basic Multilingual Plane, but it has not yet been extended to handle the current extended full Unicode (e.g., UTF-16 from UCS-2 that Tk supports).

Tk was designed to be extended, and a wide range of extensions are available that offer new widgets or other capabilities.[4][5]

Since Tcl/Tk 8, it offers "native look and feel" (for instance, menus and buttons are displayed in the manner of "native" software for any given platform).[6] Highlights of version 8.5 include a new theming engine, originally called Tk Tile,[7] but it is now generally referred to as "themed Tk", as well as improved font rendering.[8] Highlights of version 8.6 include PNG support and angled text.[9]


Tk was developed by John Ousterhout as an extension for the Tcl scripting language. It was first publicly released in 1991.[10] Tk versioning was done separately from Tcl until version 8.0.

Tk was written originally for Unix/X11, and proved extremely popular with programmers in the 1990s by virtue of its being easier to learn and use than Motif and other X11 toolkits of the time.[11] Tk was also ported to Microsoft Windows and Macintosh platforms, starting with Tk 4.2 and improved with native look and feel in Tk 8.0 (released 1997). To mark the popularity and significance of Tk in the 1990s, Ousterhout was given the ACM Software System Award in 1997 for Tcl/Tk:[12]

ACM Software System Award Winner: John K Ousterhout

For the Tcl scripting language which allows developers to create complex systems from pre-existing components. The embedded Tk provides a simple mechanism for creating graphical user interfaces. Together they make a powerful addition to the software repertoire.

Interest in Tk waned significantly from the late 1990s and onward. The default look and feel on Unix still emulated Motif, despite the mainstream replacement of Motif by toolkits such as FLTK, Qt, and GTK.[13] Widgets that became commonly used in applications (e.g. trees, combo boxes, tabbed notebooks) were not available in the Tk core, but only via multiple, often competing add-ons.[14]

Tk 8.5, released in late 2007, corrected some of these problems by adding missing widgets to the core, introducing a new theming engine and modernizing the look and feel on Unix.[8] However, because some code changes were required to incorporate these advancements, many existing applications retain the older Motif-inspired feel that Tk had become known for.[15]


Tk is a platform-independent GUI framework developed for Tcl. From a Tcl shell (tclsh), Tk may be invoked using the command package require Tk. The program wish (WIndowing SHell) provides a way to run a tclsh shell in a graphical window as well as providing Tk.[16]

Tk has the following characteristics:

Language bindings

A library written in one programming language may be used in another language if bindings are written; Tk is integrated with the Tcl language. Various other languages have bindings for Tk, a partial list of which is on the Tk website.[20] Bindings exist for additional languages which might not be listed, including Ada (called TASH),[21] Haskell (called HTk),[22] Perl, Python (called Tkinter), R (through the standard package: tcltk), Ruby, Rexx, and Common Lisp.

There are several ways to use Tk from Perl: the Tcl::Tk and Tkx Perl modules,[23] both of which use Tcl as a bridge to access Tk, and Perl/Tk,[24] which provides native Perl access to Tk structures. The Python binding uses Tcl as a bridge to Tk.[25]


Tk provides various widgets.[26] Basic widgets are embedded into toplevel widgets, which in turn are usually hosted by the operating system in floating windows that can be moved around on the screen.[27]

Basic widgets

Top-level widgets

Geometry managers

Basic widgets are arranged in toplevel windows using geometry managers:[28]

See also


  1. ^ "Tcl/Tk Core Development". Tcl Developer Xchange. Retrieved 1 November 2016.
  2. ^ "[TCLCORE] Tcl/Tk 8.6.13 RELEASED".
  3. ^ "Tcl/Tk Licensing Terms". Tcl Developer Xchange. Retrieved 4 November 2016.
  4. ^ Writing a Tk Widget in C, Chapter 46 in Practical Programming in Tcl and Tk, ISBN 0-13-038560-3
  5. ^ "Extensions for Tcl and Tk". Tcler's Wiki. Retrieved 1 November 2016.
  6. ^ "Tcl/Tk 8.0". Tcl Developer Xchange. 18 September 2013. Retrieved 1 July 2014.
  7. ^ "Tile: an improved themeing engine for Tk". SourceForge. Retrieved 4 November 2016.
  8. ^ a b "Tcl/Tk 8.5 Release Announcement". Tcl Developer Xchange. 18 September 2013. Retrieved 1 July 2014.
  9. ^ "Tcl/Tk 8.6 Release Announcement". Tcl Developer Xchange. 20 September 2013. Retrieved 1 July 2014.
  10. ^ Ousterhout, John. "History of Tcl". Tcl Developer Exchange. Retrieved 1 April 2010.
  11. ^ "Tk Backgrounder". TkDocs. Retrieved 4 November 2016.
  12. ^ "John K Ousterhout - Award Winner". ACM Awards. Retrieved 4 November 2016.
  13. ^ "TIP #48: Tk Widget Styling Support". Tcl Developer Xchange. Retrieved 1 November 2016.
  14. ^ "treeview". Tcler's Wiki. Retrieved 1 November 2016.
  15. ^ "TIP #319: Implement Backwards Compatibility for ttk Themed Widgets in tk Widgets". Tcl Developer Xchange. Retrieved 1 November 2016.
  16. ^ "wish manual page - Tk Applications". Tcl Developer Xchange. Retrieved 1 November 2016.
  17. ^ "How to Compile Tcl". Tcl Developer Xchange. Retrieved 1 November 2016.
  18. ^ "ttk::widget manual page - Tk Themed Widget". Tcl Developer Xchange. Retrieved 1 November 2016.
  19. ^ "option manual page - Built-In Commands". Tcl Developer Xchange. Retrieved 1 November 2016.
  20. ^ "Languages with a Tk binding". Tcler's Wiki. Retrieved 1 July 2014.
  21. ^ "TASH". SourceForge. Retrieved 1 July 2014.
  22. ^ "HTk home". Informatik - FB3 - Uni Bremen. Retrieved 4 November 2016.
  23. ^ "Tkx::Tutorial - How to use Tkx". ActiveState Docs. Retrieved 1 November 2016.
  24. ^ Perl/Tk Concepts, Chapter 1 in Mastering Perl/Tk, ISBN 978-1565927162
  25. ^ Tkinter, Chapter 2.4 in Modern Tkinter for Busy Python Developers, ASIN B0071QDNLO
  26. ^ "Tk Commands, version 8.6.6". Tcl Developer Xchange. Retrieved 1 November 2016.
  27. ^ Widgets', Chapter 17.2 in Tcl and the Tk Toolkit , ISBN 978-0321336330
  28. ^ Geometry Managers', Chapter 17.6 in Tcl and the Tk Toolkit , ISBN 978-0321336330

Further reading