Starting with version 2.8, released in 2005, GTK began the transition to using Cairo to render most of its graphical control elements widgets.

[3] GDK acts as a wrapper around the low-level functions provided by the underlying windowing and graphics systems.

GtkBuilder allows user interfaces to be designed without writing code.

The interface is described in an Extensible Markup Language (XML) file which is written by hand or generated by a GUI designer, which is then loaded at runtime and the objects created automatically.

[30] The most common criticism of GTK is the lack of backward-compatibility in major updates, most notably in the application programming interface (API)[31] and theming.

The compatibility breaks between minor releases during the GTK 3.x development cycle was explained by Benjamin Otte as due to strong pressures to innovate, such as providing the features modern users expect and supporting the increasingly influential Wayland display server protocol.

[33] Similarly, recent changes to theming are specifically intended to improve and stabilise that part of the API, meaning some investment now should be rewarded later.

The following window managers use GTK: For syntax highlighting there is GtkSourceView, "source code editing widget".

GtkSpell uses GTK's GtkTextView widget, to highlight misspelled words and offer replacement.

GTK was originally designed and used in the GNU Image Manipulation Program (GIMP) as a replacement of the Motif toolkit; at some point Peter Mattis became disenchanted with Motif and began to write his own GUI toolkit named the GIMP toolkit and had successfully replaced Motif by the 0.60 release of GIMP.

The GTK 2.0.0 release (2002[43]) series introduced new features which include improved text rendering using Pango, a new theme engine, improved accessibility using the Accessibility Toolkit, transition to Unicode using UTF-8 strings, and a more flexible API.

GTK version 3.0.0 (2011[44]) included revised input device handling, support for themes written with CSS-like syntax, and the ability to receive information about other opened GTK applications.

[45] HP stated that their goal was to merge the needed OpenVMS changes into the GTK Version 1.3 development stream, however this never materialised.

was the removal of user customization options (like individual keyboard shortcuts that could be set in GTK+ 2), and the delegation of functionality to ancillary objects instead of encoding it into the base classes provided by GTK.

[48] Overall support for UTF-8 The last to support Windows 98/Me Print support: GtkPrintOperation Caps Lock warning in password entry Improvements on GtkScale, GtkStatusIcon, GtkFileChooser Improvement on file chooser, printing To remove much of the necessary IPC between the X11 application and the X11 server, GDK is rewritten (mainly by Alexander Larsson) to use "client-side windows", i.e., the GdkWindow, which every widget must have, belongs now to the client Improvement on file chooser, keyboard handling, GDK Introspection data is now included in GTK Most GDK drawing are based on Cairo Many internal data are now private and can be sealed in preparation to GTK 3 The CUPS print backend can send print jobs as PDF GtkBuilder has gained support for text tags and menu toolbuttons and many introspection annotation fixes were added Migrating from GTK+ 2.x to GTK+ 3 Completed mostly Project Ridley All the rendering is done using Cairo GDK became more X11 agnostic XInput2, theme API is based on Cascading Style Sheets (CSS), worsening the achievable performance for 60 Hz frame rates New Font Chooser dialog New experimental backends: A new color chooser Added support for touch devices Added support for smooth scrolling GtkScrolledWindow will do kinetic scrolling with touch devices macOS support is improved This is the first version of GTK 3 that works well on Windows The Wayland backend is updated to the current Wayland version Spin buttons have received a new look Accessibility: the treeview accessible support is rewritten More complete CSS theming support Vertical spin buttons CSS animations, blur shadows Support for cross-fading and transitions in themes Support for the broadwayd server Improved theming Better geometry management Touch improvements Support with the window manager for the frame synchronization protocol GdkFrameClock added[73] Support for Wayland 1.2 Added: Removed: Tear-off menu-items, plus many GTK settings The modern GTK drawing model Support for Wayland 1.5 New widget: GtkPopover (an alternative to menus and dialogs) Improved support for gestures/multi-touch merged[80][81] Deprecated:[82] Most widgets converted to use gestures internally Wayland supports GNOME Shell classic mode[83] New widgets: Scrolling overhauled (scrollbar hidden by default[85]) Experimental Mir backend[86] More filechooser design refresh and better filechooser search Dropped Windows XP support Model support for list and flow box Kinetic touchpad scrolling Touchpad gestures (Wayland) gtk-builder-tool utility Output-only windows Move drag and drop down to GDK New widget: GtkShortcutsWindow (shows keyboard shortcuts and gestures of an application) Wayland tablet support is merged,[91] support for graphics tablets is considered feature complete[92] GTK 3.22 shall be as rock-stable (and hence "boring") as GTK 2[33][93][94] Dependency bumps – require: New font chooser features: New Emoji features: Other new APIs: gdk_window_move_to_rect Wayland: use anonymous shared memory on FreeBSD Backported event controllers from GTK 4: Deprecate a few APIs that are gone in GTK 4: 3.24.29 Remove any API marked as deprecated Heavy development A new Vulkan-renderer augments the old Cairo-renderer[97] 3.89.2 3.89.4 3.89.5 3.90 GNU autotools was replaced with Meson.