Dia is described as «GTK+ based diagram creation program for Linux, Unix, Mac OS X and Windows released under the GPL license» and is a very popular Diagram Editor in the business & commerce category. There are more than 50 alternatives to Dia for a variety of platforms, including Windows, Online / Web-based, Linux, Mac and Chrome OS. The best alternative is diagrams.net, which is both free and Open Source. Other great apps like Dia are yEd Graph Editor, LibreOffice — Draw, Penpot and PlantUML.Dia alternatives are mainly Mind Mapping Tools but may also be Diagram Editors or Vector Graphic Apps. Filter by these if you want a narrower list of alternatives or looking for a specific functionality of Dia.