Outlook OST File Location: Where to Find OST Files in Windows 10/11
Quick Answer: The default Outlook OST file location in Windows is:
C:\Users\<username>\AppData\Local\Microsoft\Outlook
You can also find the exact location in Classic Outlook >> File >> Account Settings >> Account Settings >> Data Files >> Open File Location. Microsoft confirms that Offline Outlook Data Files (.ost) are normally stored in the user’s AppData\Local\Microsoft\Outlook folder.
Tip: In File Explorer, you can enter %localappdata%\Microsoft\Outlook in the address bar to open the default folder directly.
Outlook OST File Location by Version
For supported versions of Classic Outlook for Windows, the default OST location is generally the same. Still, you can check it as per your Outlook version.
| Outlook Version | Typical OST File Location |
|---|---|
| Outlook 2010 | C:\Users\<username>\AppData\Local\Microsoft\Outlook |
| Outlook 2013 | C:\Users\<username>\AppData\Local\Microsoft\Outlook |
| Outlook 2016 | C:\Users\<username>\AppData\Local\Microsoft\Outlook |
| Outlook 2019 | C:\Users\<username>\AppData\Local\Microsoft\Outlook |
| Outlook 2021 | C:\Users\<username>\AppData\Local\Microsoft\Outlook |
| Outlook 2024 | C:\Users\<username>\AppData\Local\Microsoft\Outlook |
| Microsoft 365 Classic Outlook | C:\Users\<username>\AppData\Local\Microsoft\Outlook |
| New Outlook for Windows | Storage differs from Classic Outlook; New Outlook does not use the same traditional OST file storage as Classic Outlook. |
What about New Outlook for Windows?
New Outlook for Windows doesn’t work quite the same way as Classic Outlook with OST files. So if one is using New Outlook, they should not assume their mailbox data is stored in a normal, accessible .ost file at:
C:\Users\<username>\AppData\Local\Microsoft\Outlook
In Classic Outlook, an OST file is a cached version of mailbox data that is stored locally. Users can access this through File >> Account Settings >> Data Files.
The structure design of new Outlook storage is different, so the traditional OST file location instructions might not be applicable.
Method 1: How to Find the OST File Location from Outlook
If you use Classic Outlook, you can easily find out the exact location of OST without looking for it manually through Windows folders.
Note the following steps:
- Launch Outlook.
- Click on File.
- Choose Account Settings.
- Click Account Settings again.
- Click the Data Files tab.
- Choose the account that is associated with the OST file.
- Select Open File Location.
Outlook will open the folder that contains the selected data file. Microsoft also describes the Data Files section as a way of determining the Outlook data files for accounts.
Why use this method? This is a commonly used method to find OST file in Outlook. It also helps confirm that the file you found is actually associated with the Outlook account you are using.
Method 2: How to Find the OST File in File Explorer
If you know that Outlook is using the default OST location, you can go to it directly in File Explorer.
#1. Via the Local AppData Shortcut
- Open File Explorer by pressing Windows + E.
- Click on the address bar.
- Enter: %localappdata%\Microsoft\Outlook and click Enter.
- Search for files with the suffix .ost.
The shortcut opens the local Outlook folder of the current Windows user.
#2. Manual Browsing
You can also look through:
C:\Users\< username >\AppData\Local\Microsoft\Outlook
Change <username> to your Windows account name.
Method 3: Locate OST File Using Windows Search
If you can’t find the OST file manually, try searching for it:
- Press Win + S to open Windows Search.
- Type .ost and press Enter.
- Windows will display all OST files available on your system.
- Right-click the file and select Open File Location to access it.
Therefore, if you follow the above steps then you will be able to find the location of Outlook OST file without facing any issues.
What is an OST File and How is it Different from PST?
OST (Offline Outlook Data File) is a local copy of mailbox information that Outlook uses to work with synchronised data when offline. Microsoft says that OST files are copies of data that resides on the mail server.
But a PST, or Outlook Data File, is different. PST files are used to create local Outlook data files, archive, export mailbox data, and transfer or back up supported Outlook items.
| Feature | OST | PST |
|---|---|---|
| Full name | Offline Outlook Data File | Outlook Data File |
| Main purpose | Cached/synchronized mailbox data | Local storage, archive, export |
| Usually associated with | Exchange/Microsoft 365 and supported account configurations | Archives, exports, and supported POP/data-file scenarios |
| Server synchronization | Yes, for supported accounts | No automatic mailbox synchronization |
| Standalone use | Not designed as a normal portable mailbox file | Can be opened as an Outlook data file |
| Common extension | .ost | .pst |
Important: Don’t automatically consider an OST a backup file. It is a synchronised copy of your Outlook profile data stored on the server. Microsoft stated that it can be recreated when the account is reconfigured.
How to Change the OST File Location?
If your default drive is running out of space, you might want to have Outlook create an OST file in a different location.
Microsoft documents the ForceOSTPath registry setting as a way to change the location where a new OST file is created for supported Classic Outlook configurations. The important caveat is that ForceOSTPath applies to a new Outlook profile.
Steps to Change the OST Location Using ForceOSTPath
- Close Outlook.
- Press Windows + R.
- Type regedit and hit Enter.
- Go to: HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Outlook\AutoDiscover
- Right-click on Outlook.
- Choose New >> Expandable String Value.
- Name the value: ForceOSTPath
- Double-click on ForceOSTPath.
- Type the full path to the folder where you want the new OST file created, for example: D:\Outlook\OST
- Click OK.
- Open Registry Editor.
- Create or configure a new Outlook profile if necessary.
Microsoft explicitly warns that incorrect changes to the Registry can cause problems, so back up the Registry before you make any changes.
Can I just transfer my existing OST?
There is a difference between moving the OST location and moving an existing OST permanently and expecting Outlook to keep using it automatically.
Microsoft’s documented ForceOSTPath method for a new Outlook profile. Depending on the Outlook configuration, creating a new OST may cause Outlook to re-download synchronised mailbox data.
So, do not delete the existing OST unless you are sure that your mailbox data is available on the server and the new Outlook profile is working fine.
Is Your OST File Huge or Corrupted?
An OST file can grow very large as Outlook caches a lot of mailbox data locally.
In Classic Outlook, you can control how much of your Exchange or Microsoft 365 mail is saved offline with:
File >> Account Settings >> Account Settings >> Choose Account >> Change >> Offline Settings.
Available period can be All, 12 months, 6 months, 3 months or 1 month, depending on the version and configuration of Outlook.
If the OST looks corrupt
Microsoft says for Exchange accounts, Outlook can rebuild the offline OST after it’s deleted and the account is reopened. Since the OST is a synchronised copy, the mailbox data can be downloaded again from the server.
But, do not delete an OST on a whim when you are not sure if the required information is available on the server.
And what about Scanpst?
Microsoft provides the Inbox Repair tool, SCANPST.EXE, to diagnose and repair errors in Outlook data files. But Microsoft’s current repair guidance focuses on its repair workflow for PST files. Microsoft also documents deleting and recreating the offline OST as appropriate for an Exchange account using an OST.
How to Get Emails from an Old or Orphaned OST File
If you can’t open your OST file due to corruption or other issues, Advik OST to PST Converter is the perfect solution. This tool helps you repair damaged OST files and convert them into PST format, so you can access your emails, contacts, calendar, and other data. With its simple and easy-to-use interface, you can fix OST file problems quickly and keep your data safe and accessible.
Final Words
For Classic Outlook on Windows, the usual OST file location is:
C:\Users\<username>\AppData\Local\Microsoft\Outlook
The quickest way to confirm the exact file is File >> Account Settings >> Account Settings >> Data Files >> Open File Location. If you have an old or orphaned OST and need to recover its mailbox contents, you may need an OST to PST conversion solution rather than simply opening the file in Outlook.
Frequently Asked Questions
Q1. Is an OST file an Outlook data file?
Ans. Yes. The OST is the Offline Outlook Data File. It maintains a synchronised local copy of supported mailbox information to allow Outlook to work with the data offline.
Q2. Can I delete an OST file?
Ans. For supported Exchange accounts, Outlook can recreate an OST file after it’s deleted. But make sure you have the mailbox data you need on the server and that Outlook is closed before you delete the file. Microsoft has documented how to recreate an OST as part of their troubleshooting guidance.
Q3. Can I open an OST file without Outlook?
Ans. An OST is not a PST that you can just open on its own. If the original account or Outlook profile is unavailable and you need the contents of an old OST, an OST extraction/conversion solution may be necessary.
