OmniGraffle is described as 'can help you make eye-popping graphic documents—quickly—by providing powerful styling tools, keeping lines connected to shapes even when they’re moved, and magically organizing diagrams with just one click' and is a well-known app in the Office & Productivity category. There are more than 50 alternatives to OmniGraffle for a variety of platforms, including Windows, Mac, Online / Web-based, Linux and iPad. The best alternative is diagrams.net, which is both free and Open Source. Other great apps like OmniGraffle are Pencil Project (Free, Open Source), yEd Graph Editor (Free), LibreOffice - Draw (Free, Open Source) and Dia (Free, Open Source).
Penpot is the first Open Source design and prototyping platform meant for cross-domain teams. Non dependent on operating systems, Penpot is web based and works with open web standards (SVG). For all and empowered by the community.
Google Drawings, part of Google Drive, allows users to collaborate creating, sharing, and editing images or drawings. It can be used for creating charts, diagrams, designs, flow-charts, etc. It contains a subset of the features in...
Graphviz is open source graph visualization software. It has several main graph layout programs. It also has web and interactive graphical interfaces, and auxiliary tools, libraries, and language bindings.