Excalidraw
Virtual whiteboard for hand-drawn diagrams
Free124.9K
Sketch Measure
Sketch redline plugin. Annotate distance and size of elements.   
Alternatives to Sketch Measure
MarkText
Next generation markdown editor, running on platforms of MacOS Windows and Linux. [![Open-Source Software][OSS Icon]](https://github.com/marktext/marktext) ![Freeware][Freeware Icon]
Open Source57.1K
Penpot
Open-source design and prototyping platform
Open Source49.4K
tldraw
Infinite canvas drawing tool
Free47.6K