What is a .one file?
Microsoft OneNote Section File · Document · Microsoft · 2003
A .one file is a Microsoft OneNote section: a container of free-form notebook pages with text, ink, images and attachments. Sections live inside a notebook folder alongside a .onetoc2 table of contents.
What is a .one file used for?
OneNote stores each notebook section as its own .one file in the MS-ONESTORE format, a revision-based store that starts with a fixed 16-byte GUID. Pages inside are free-form canvases, which is why nothing else renders them faithfully.
Modern OneNote increasingly keeps notebooks in the cloud, so loose .one files usually come from backups or old local notebooks. OneNote for Windows opens them directly via File > Open.
What opens a .one file?
The .one format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- Microsoft OneNote
- OneNote for the web (after import)
macOS
- Microsoft OneNote (import)
- OneNote for the web
Linux
- OneNote for the web (after import to OneDrive)
Open a .one file step by step
- Confirm the file really is a .one. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with Microsoft OneNote or OneNote for the web (after import).
- On Mac, use Microsoft OneNote (import) or OneNote for the web.
- On Linux, try OneNote for the web (after import to OneDrive).
- Still stuck? Convert the .one to pdf, which opens more widely.
Why can't I open my .one file?
Almost always because no installed app understands OneNote. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .one at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
How to convert a .one file
You can convert a .one file to pdf, docx using a conversion tool or the export menu of an app that opens it.
What is the .one file signature (magic bytes)?
A .one file starts with the hex bytes E4 52 5C 7B 8C D8 A7 4D AE B1 53 78 D0 29 96 D3, which read as .R\{...M..Sx.).. in ASCII. Programs identify OneNote by those bytes, not by the filename, so a renamed file still gives itself away.
These are the documented signatures for OneNote. For a full breakdown, see the OneNote file signature page.
| Hex signature | Offset | ASCII | Note |
|---|---|---|---|
| E4 52 5C 7B 8C D8 A7 4D AE B1 53 78 D0 29 96 D3 | 0 | .R\{...M..Sx.).. | OneNote section GUID |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .one file?
A .one file is a Microsoft OneNote section: a container of free-form notebook pages with text, ink, images and attachments. Sections live inside a notebook folder alongside a .onetoc2 table of contents.
How do I open a .one file?
In OneNote on Windows use File > Open and pick the file, or place it back in its notebook folder. On other platforms, import the notebook into OneDrive and open it with OneNote for the web.
What is the difference between .one and .onetoc2?
Each .one file is one section of a notebook; the .onetoc2 file is the notebook's table of contents that tells OneNote which sections belong together and in what order.
Can I convert a .one file to PDF or Word?
Yes. Open the section in OneNote and export the section or individual pages to PDF or DOCX from the File menu.
Related formats
Sources
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