Some free alternatives to Microsoft Visio are yEd, Calligra Flow and Draw.io. YEd is compatible with Windows, Mac OSX and Linux. It lets users create diagrams from scratch or import data in XLS or XML format for analysis. It arranges the elements in a diagram automatically.
Calligra Flow is part of the Calligra Suite, and it is compatible with Windows, Mac OSX, Linux and FreeBSD. This software lets users create diagrams and flowcharts including network diagrams and organization charts. Draw.io is a web-based tool for creating diagrams. Users can choose to save files on a hard drive or at one of the cloud storage services including Dropbox, Google Drive or OneDrive.