What Is Inside a .drawio File
A .drawio file is XML text written by Draw.io, the diagram editor also known as diagrams.net. Each page is a diagram element listing shapes, connectors, labels, and styles. Newer versions save plain XML, while older ones compress each page, which is why some files look like random characters.
Opened in a code editor, the file shows markup rather than a picture. A Drawio viewer reads the XML and draws it with the original engine, so you see the diagram instead of its source. The .dio extension and many .xml exports use the same format.
