On April 9, 2019, Microsoft identified a code issue that allowed locally stored OneNote notebooks to be imported and edited in OneNote for Windows 10 without connecting the notebook to the cloud. In this unsupported state, a user's changes to the notebook are stored only in the OneNote cache. The cache will be lost if the user uninstalls OneNote for Windows 10. In OneNote versions prior to 16.0.11601.20066.0, opening an older version of the local notebook will cause more recent changes in the cache to be lost.
Microsoft treats customer data integrity with the utmost importance, and while cached data may have been affected by this issue, no data belonging to you or your organization was exposed to third parties as a result of this event. We investigated all forms of recovery and affected scope. Unfortunately, there isn’t a solution to recover notebooks if OneNote for Windows 10 was uninstalled or if an older version of the notebook was opened in OneNote for Windows 10.
Note: Keep in mind that the latest version of OneNote for Windows 10 prevents older versions of a notebook from being opened and overwriting the cache.
For notebook data that’s in the OneNote Windows 10 cache, we’ve created instructions to recover this data.
Recovering OneNote data manually
Follow these instructions to manually recover a OneNote 2016 or prior notebook that may have become lost when opened in OneNote for Windows 10.
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In File Explorer, go to:
C:\Users\[user name]\AppData\Local\Packages\Microsoft.Office.OneNote_8wekyb3d8bbwe\LocalCache
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[user name] is your Windows login name.
Each folder name is a notebook's name.
Tip: Make sure you can see hidden folders. In Windows Explorer, on the View tab, select Hidden items.
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Open a new File Explorer window. On the File menu, click Open new window.
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Go to your Documents folder, and then create a new folder, such as OneNoteBackups (recommended).
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Copy all OneNote folders from step 1 to the OneNoteBackups folder created in Step 3.
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Open OneNote 2016. In the notebook list for OneNote 2016, close every notebook that matches the name of a folder in Step 1. In the notebook list, right-click the notebook name, and then click Close this notebook.
Note: If you don't have OneNote 2016, you can install it here.
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In OneNote 2016, go to File > Open > Browse.
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Browse to the Documents\OneNoteBackups folder. Click into a folder and open the .onetoc2 file. Repeat this for every folder under OneNoteBackups.
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Now every notebook that's recoverable should be opened in OneNote 2016. Each notebook should have your most recent changes. You can now continue to edit these notebooks in OneNote 2016.
Automatically copy OneNote data (optional)
You can use a deployable PowerShell script to automate steps 1-4 above. The script is located here.
Keep the following in mind when using this script:
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PowerShell must be allowed to run on the PC.
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This script will only work if run by a user or if run as a user when deployed.
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The new backup folders created will have English names, whereas the notebooks will remain in the original language.
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After running the script, any recoverable data will be copied to the user's My Documents\OneNoteBackups\Backup_<date> folder.
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You can run the script more than once. Every time you run it, another backup with a different date stamp in the name will be created.
Important: This script may fail to copy all data if OneNote for Windows 10 is open. The script closes OneNote but a user could open it before copying is done.
