.ONETOC File Extension

A ONETOC file is an index file created by Microsoft OneNote 2003, a program used to take notes and journal. It contains information about the ordering of different note-taking sections. ONETOC files are used for organizing the collection of notes in the notebook.

ONETOC files are created by OneNote when you create a OneNote notebook by selecting File → New in OneNote. ONETOC files are not meant to be manually opened. It is instead referenced by OneNote when opening a notebook. If you delete the ONETOC file, OneNote will display the notebook sections in alphabetical order, which you can manually reorder.

NOTE: ONETOC files are used by Microsoft OneNote 2003. The file was replaced by .ONETOC2 with the release of OneNote 2007.