How to open the OneNote cache file

Summary:EverNote is great for using on smartphones but for keeping track of anything and everything on my PC, I love OneNote. I can write on my tablet screen and have my handwriting recognised, I can record audio that's time-synced to my typed notes, I can clip in sections of Web pages or dialog boxes I want to use as screen grabs, I can print in documents to annotate...

EverNote is great for using on smartphones but for keeping track of anything and everything on my PC, I love OneNote. I can write on my tablet screen and have my handwriting recognised, I can record audio that's time-synced to my typed notes, I can clip in sections of Web pages or dialog boxes I want to use as screen grabs, I can print in documents to annotate... I put everything in OneNote.

And I've never lost anything because OneNote never makes you save a file by hand. It autosaves everything into a local cache file every few seconds, backs that up to another local file (by default once a day) and then syncs the changes to the master notebook - which can be on your PC, on a server, on SharePoint, on a cloud storage service that you map as a drive, on a USB stick or on SkyDrive (where I can view or edit the notebook in the browser) or anywhere else you can connect to - as soon as it's available. You can make changes offline and they're just magically updated when you get back online - so I can take notes on my teeny tiny VAIO Series P over lunch then read them on my big-screen big-keyboard Dell Studio when I want to work with them (or write them on my big keyboard and refer to them on my VAIO). If you only use OneNote on one PC, you end up with three levels of local backup; but most people who use OneNote share notebooks between PCs, so that local caching is even more useful. You can get at the backup files using Help > Open Backups in OneNote 2007 or by clicking the Open Backups button on the Backstage menu in OneNote 2010 (click File then Open Backups).

What you find in your backup may not be enough if you get the rare error message that tells you the cache is corrupted and OneNote has to delete it, rebuild it and throw away any unsynced data. This happened to me a few times thanks to an interaction between OneNote 2007 and the beta version of OneNote 2010 (again - this is why it's called beta software) and it's fixed in the shipping version so I haven't had this problem myself in months, but I've seen the odd question about this online recently so I wanted to list what worked for me.

Usually the error was on a machine that had a secondary copy of the notebook, not one with unsynced changes so I just let it rebuild and carried on working.

Once I got the error before I'd had a chance to sync and I knew there was one page that I would have lost. I grabbed the original .ONECACHE file, and while I worked out how to open it, tried a workaround; right-click on the section in OneNote and save it out. It takes good timing but, with the mouse in the right area of the screen, I could right-click, choose Save As and get a copy of the notebook before the message about deleting the cache came up (NOTE - at no point did I click on the option to delete the cache; once you do that it's gone for ever).

This works but there's one thing to be aware of. My plan was to open the copy of the notebook in OneNote on another PC and copy the pages I needed into the original section on that machine and then delete the cache. OneNote isn't like Excel - it's perfectly happy to open as many files and sections with the same name as you can keep straight in your head. But when you open the file it's important to click Open Section instead of following OneNote's advice to open the notebook - as that opens the folder the .ONE file is in, including any folders nested beneath it.

If you've put the copy of the .ONE file in a root directory in your hurry to save it somewhere before the dialog popped up again, you get a notebook with all the folders on the drive as sections and OneNote grinds to a halt. The good news is that with Windows 7 and OneNote 2010 , even though the spinning stargate of doom appears repeatedly, the app keeps working; scrolling through the list of tabs to right-click on the unwanted notebook and choose Close was taking rather too long but I was able to click File for the backstage menu, scroll down to the notebook in the intervals between the spinning busy cursor, click the Settings button and choose Close. Then I could open just the section, get my pages and get back to work.

If you do it right in the first place, you get a copy of your notebook that you can get your pages from so you can delete the corrupt cache and let OneNote rebuild it.

If that doesn't work, or you have an old .ONECACHE you need to open, here's how to do it.

If you've just noticed the problem and don’t already have a copy of the cache file, copy the file into another folder (or right-click it in Explorer and choose Copy and then Paste to get a copy in the same folder that you can move). The sooner you take he copy the more likely you are to recover your pages; you need to get it before the cache has been optimised - at that point the deleted pages get optimised away and they're gone .

Change the file extension from .ONECACHE to .ONE.

Use the Search box in the Start menu (in Vista and Windows 7) or the Run box (Windows-R) or the CMD prompt (you may need to be in the OneNote install folder) to type in this command: onenote /forcerepair "path" Where "path" is the path to the folder with the copy of the cache that you've changed the extension on.

OneNote will repair the file; you'll get a couple of dialog boxes warning you OneNote has to restart and suggesting you review the notebook - you may also have to open the repaired file in OneNote again. When you do, you get a single section with a flat list of all the pages in all of the notebooks that were in the cache; search for the recent pages t that you know hadn't synced and you can move them back into the rebuilt original notebook (remember - the reason you're doing this is that you know there is a page that won't have been synced to the master copy).

If you want to look for recent pages - in a rebuilt notebook or across multiple notebooks - I can recommend the excellent (and free) OneNote Calendar. This gives you a calendar view with all the notes you created or changed on a particular day listed by day, week or month. (It's a OneNote 2007 add-in that I've had no problem using in OneNote 2010 but it is getting an official update for OneNote 2010). The only thing that isn't perfect about the add-in is that if I edited a page last week it shows up last week - not in August 2008 when I first started taking notes on the page. I want the option to see all the pages I first created on a specific date - a date that's shown at the top of the page - but neither OneNote's own search nor Calendar has creation date as an option. If anyone knows why, I'd love to hear about it.


Topics: Windows


Born on the Channel Island of Jersey, Simon moved to the UK to attend the University of Bath where he studied electrical and electronic engineering. Since then a varied career has included being part of the team building the world's first solid state 30KW HF radio transmitter, writing electromagnetic modelling software for railguns, and t... Full Bio


Mary Branscombe is a freelance tech journalist. Mary has been a technology writer for nearly two decades, covering everything from early versions of Windows and Office to the first smartphones, the arrival of the web and most things inbetween.

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