Dia is a general-purpose diagram and schematic drawing application. It can be used for UML diagrams as well as flowcharts, network layouts, entity relationship diagrams, circuits and many other forms of structured illustration.
Rather than being restricted to UML, Dia provides collections of reusable objects for different diagramming tasks. Additional shapes can be defined using XML, making the application useful for specialised diagram sets as well as general documentation.
This is free and open source software.
Key Features
- UML diagram objects.
- Entity relationship diagrams.
- Flowcharts and network diagrams.
- Electrical and other schematic object sets.
- Extensible shape libraries.
- Layer support.
- Custom XML-based diagram format.
- Import and export facilities for numerous graphics and diagram formats.
- Command-line operation.
- Multi-page printing.
- Scripting facilities.
Website: gitlab.gnome.org/GNOME/dia
Support:
Developer: Dia Developers
License: GNU General Public License v2.0

Dia is written in C. Learn C with our recommended free books and free tutorials.
Related Software
| Unified Modeling Language tools | |
|---|---|
| Eclipse Papyrus | Edit models based on UML and related languages |
| PlantUML | Draw UML diagrams from simple textual description |
| Mermaid | Generate diagrams from markdown-like text |
| Umple | Create UML models textually |
| Modelio | UML and BPMN modeling environment |
| Gaphor | Simple UML and SysML modeling tool |
| Umbrello | UML Modeller based on KDE technology |
| UMLet | Java-based UML tool |
| JetUML | Sketch software design ideas with a minimum of fuss |
| Violet | Designed for people who need to produce simple UML diagrams |
| Dia | GTK+ based diagram creation software |
| ArgoUML | UML modeling tool |
| crystal-facet-uml | Desktop UML and SysML modeling application |
| UML Designer | UML tool based on Sirius and Eclipse |
Read our verdict in the software roundup.
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Dia is indeed good and I have seen so many users recommended it. Do you know whether the tool can export /import vsdx or vsd files? I’m using Visio 2016 pro sometimes so I may need to export vsdx files to other diagramming tools.
So far, the one I found recently that can export vsdx and vsd files is Edraw Max 9.4, but it is not free if you need to edit your files (only open and view are totally free).
Why don’t you try Dia and report back if it can export / import the file types you want?