IUP review
A free native UI toolkit for C and Lua desktop apps on Windows and Linux.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
IUP is a free toolkit for building desktop graphical interfaces in C, Lua or LED. Its audience is developers who want controls, dialogs and layouts for Windows and Linux applications, particularly those working in C or Lua. The toolkit provides buttons, lists, text fields, menus and canvases, alongside tabs, a matrix control and an OpenGL canvas. Predefined dialogs cover file selection, messages and data input, giving projects common interface elements without requiring every dialog to be specified from scratch.
IUP's interface model combines native elements on supported platforms with an abstract box-and-glue layout system. Its backends include GTK+, Motif and Windows, and the toolkit is intended to let applications run across supported systems with minimal platform-specific changes. Developers can create and manipulate dialogs through the C API, use the Lua binding for UI development, or describe dialogs in LED. This mix suits teams that value those languages and a native desktop UI approach; it is a narrower fit for projects seeking mobile targets or a broader platform range.
The main qualification is the project's maintenance status: regular development has been on hold since 2023, with work limited to small bug fixes and changes and no timeline for a return. That makes IUP a more suitable consideration for developers comfortable evaluating a toolkit with limited ongoing maintenance than for teams that require active development or commercial support. It remains free software and can be used in public and commercial applications. Developers who need a C or Lua toolkit for Windows and Linux may find its control set and layout model relevant; those prioritizing regular development or mobile deployment should look elsewhere.
IUP pros and cons
- Where it wins
- Free software usable in public and commercial applications
- Offers C, Lua and LED paths for building interfaces
- Includes native controls, layout tools and predefined dialogs
- Where it doesn't
- Targets Windows and Linux rather than mobile platforms
- Regular development has been on hold since 2023
- Maintenance is limited to small bug fixes and changes
IUP fact sheet, pricing and score →
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