What is a UI file?
A .UI file is a User Interface File primarily developed by the Qt Group. Developers use Qt Designer to create visual layouts for desktop and mobile applications. The file saves the placement of buttons, text boxes, menus, and other visual widgets in a structured XML format.
Other types of UI files
Because the extension simply stands for 'User Interface', .UI has multiple possible meanings. These files can store game layouts for engines like Angelica 3D, Eternity Engine, or Cocos2d-x. In other cases, they act as user interface skin packages (saved internally as ZIP files) for 360 Total Security or as layout customizations for PTC Creo Parametric. Some hardware systems, like Thinget HMI, even use .UI files compiled as executables.
How to open UI files?
If you know your file is a standard layout, you can open it with Qt Creator or any basic text editor. However, if you are unsure what kind of file you have, viewer.online/ui analyzes .UI files to identify their exact format and creator software. It shows which programs can open the file and usually previews it directly in your browser.
Software and tools
For software development, engineers use command-line tools like `pyuic5`, `pyuic6`, or `pyside6-uic` to convert Qt .UI files into functional Python code. For standard viewing without specialized development tools, you can simply read the raw XML structure. If you need the layout data in a different format, we recommend using convert.guru to convert .UI text to .PY, .CPP, or .TXT.
Summary
Because standard .UI files use the known XML format, viewer.online/ui can safely open and display them online, eliminating compatibility problems. If your file comes from a different program or game engine, our tool will safely identify the actual format of your file so you know exactly how to handle it.