Where Does Outlook Store OST and PST Files?
Outlook OST and PST locations on Windows and Mac, and which one you can actually move to a new PC.
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On Windows, Exchange and Microsoft 365 accounts use OST files under Local AppData. POP archives and manual backups use PST files under Documents, then Outlook Files.
Only PST files move cleanly between computers. OST files rebuild from the server when you add the account, so copying them across is pointless.
Where Outlook stores this, by platform
%LOCALAPPDATA%\Microsoft\Outlook
OST files for Exchange, Microsoft 365 and IMAP live here. PST archives live separately under %USERPROFILE%\Documents\Outlook Files. Paste either path into File Explorer.
~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles
Mac Outlook uses a profile database here instead of loose OST and PST files. In Finder use Go > Go to Folder. Do not relocate it by hand; export from inside Outlook instead.
Frequently asked questions
Can I move an OST file to a new computer?
There is no point. Add the account on the new PC and Outlook rebuilds the OST from the server. Move PST files instead; those hold portable POP mail and archives.
Why is my Outlook folder using tens of gigabytes?
That is usually the OST cache of a large mailbox plus attachments. Shorten the cached mail slider in Account Settings or compact archives into a PST.
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