[zaynb]

Draw.io is free and open source. Online, Mac, Windows, Linux.

Online: https://www.draw.io/

Desktop: https://github.com/jgraph/drawio-desktop/releases/

Example diagrams: https://about.draw.io/features/examples/

Source code: https://github.com/jgraph/drawio

[dangoor]

Draw.io is great, but it's not the same as OP. It's a drawing tool rather than a text -> diagram tool.