UXF is an extension given to files by a specialized diagramming software called UMLet. UXF are files used to store projects made in the program. Most often, this solution is used to create models of IT systems and business processes. UXF is a format that is based on XML and is a format for exchanging UML diagrams.

UMLet is an application that works alone or as a plug-in in the Eclipse integrated development environment. It can be used on Windows, OS X and Linux.