OneNote
From Just Solve the File Format Problem
OneNote is a Microsoft application for note taking and similar tasks, with a focus on multi-user collaboration.
Most editions have a native .one file format. It's not clear, but some cloud-only editions might not have any way to save to a local file at all (though you could maybe still Print to a file).
Identification
Some or all .one files begin with bytes E4 52 5C 7B 8C D8 A7 4D AE B1 53 78 D0 29 96 D3. This represents the GUID {7B5C52E4-D88C-4DA7-AEB1-5378D02996D3}, which is a code for the file type.
.onetoc2 files begin with A1 2F FF 43 D9 EF 76 4C 9E E2 10 EA 57 22 76 5F.
.onepkg is based on Cabinet format.
