Diagrams.net (formerly draw.io) is a free, open-source diagramming application. It supports a wide variety of diagrams including flowcharts, UML, entity relationship diagrams, network diagrams, and more. Diagrams can be created directly in your browser or downloaded for offline use. It integrates with various platforms like Google Drive, OneDrive, and Dropbox, allowing for easy storage and collaboration. Users can import and export diagrams in multiple formats, such as SVG, PNG, JPEG, and PDF.