Apps similar to QDia include LibreOffice - Draw, which is free and open source. Other options are Dia, yEd Graph Editor and QElectroTech. In total there are four Diagram Editors like QDia for Mac, Windows, Linux and the web.
Draw lets you produce anything from a quick sketch to a complex plan, and gives you the means to communicate with graphics and diagrams. With a maximum page size of 300cm by 300cm, Draw is a an excellent package for producing technical drawings, general posters, and much else.
Germany
EU
Open-source diagram editor supporting Linux, Windows, Unix, and Mac OS X, with features for constructing entity relationship, UML, flowchart, and network diagrams, customizable with XML-defined shapes, extensibility, and a GTK+-based graphical user interface.
United States
yEd is a powerful diagram editor that can be used to quickly create diagrams manually or import external data for analysis and auto-magically arrange even large data sets by just pressing a button. You can use yEd to quickly create flow charts, BPMN and UML diagrams...
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QElectroTech is a free software to create electric diagrams. QElectroTech is under GNU/GPL license. It is currently available for Windows, Mac OS and Linux.
