How to Clear the Outlook Cache on Mac and Shrink the Profile Database (2026)

Microsoft Outlook for Mac is one of the heaviest email clients on the platform. A moderately active mailbox can quietly grow its on-disk footprint to 10, 20, even 40 gigabytes over a year or two, most of it spread across a cache folder and a SQLite profile database that Outlook never compresses on its own. If you have noticed "Outlook" appearing near the top of your Storage screen, or if Outlook is taking up space on Mac that you cannot explain, this guide walks you through every layer: what those files actually are, how to clear them safely, and how to keep the database lean going forward.

Why Outlook Accumulates So Much Space

New Outlook for Mac (the version that ships with Microsoft 365 as of 2025-2026) stores data in two main places:

• Group Containers cache: ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/ holds the main profile database (Outlook.sqlite), attachments, and a large cache of synced mail bodies.
• Application Support: ~/Library/Application Support/Microsoft/Outlook/ stores preference files and supplemental caches.
• Caches folder: ~/Library/Caches/com.microsoft.Outlook/ holds rendered content, thumbnails, and network response caches.

The Group Containers path is the one that surprises people. Because it sits outside the usual ~/Library/Caches tree, most cache-clearing guides miss it entirely. Outlook re-downloads and re-indexes mail bodies from Exchange or IMAP as needed, so the cache folder is genuinely safe to clear, with one caveat covered below.

Before You Start: Quit Outlook Completely

All of the steps below require Outlook to be fully closed. A background sync will lock the database and can corrupt it if you delete files while it is running.

1. Click the Outlook icon in the Dock.
2. Choose Outlook > Quit Outlook from the menu bar (or press Command-Q).
3. Check the menu bar for the Outlook icon. If it persists, right-click it and choose Quit.
4. Wait a few seconds, then confirm Outlook no longer appears in Activity Monitor.

Step 1: Clear the Main Cache Folder

Open Finder, press Command-Shift-G, and paste the following path:

~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile/Data

Inside you will find a folder called Attachments and one called Cache. The Cache folder contains locally stored message bodies synced from the server. You can move its contents to the Trash. Outlook will re-download messages as you open them.

If you prefer Terminal, run:

rm -rf ~/Library/Group\ Containers/UBF8T346G9.Office/Outlook/Outlook\ 15\ Profiles/Main\ Profile/Data/Cache/*

Note on Attachments: Do not delete the Attachments folder wholesale. Outlook stores some locally composed draft attachments here that have not yet been sent. Open the folder, sort by date modified, and remove only files older than a month or anything you recognize as an old download.

Step 2: Clear the Standard Caches Folder

This is the traditional macOS cache path and is safe to clear in full while Outlook is closed:

rm -rf ~/Library/Caches/com.microsoft.Outlook

Outlook will rebuild this folder the next time it launches. On a large mailbox the rebuild may take a minute or two.

Step 3: Shrink the Outlook Profile Database

The Outlook profile database on Mac is a SQLite file called Outlook.sqlite located at:

~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile/

SQLite databases accumulate empty pages over time as rows are deleted. The file size does not shrink automatically. Running VACUUM compacts the database and can reclaim several gigabytes on a large, long-lived account.

1. Confirm Outlook is still closed.
2. Open Terminal (/Applications/Utilities/Terminal.app).
3. Run the following two commands in order:

cd ~/Library/Group\ Containers/UBF8T346G9.Office/Outlook/Outlook\ 15\ Profiles/Main\ Profile/
sqlite3 Outlook.sqlite "VACUUM;"

On a database that has grown to 8-12 GB, this command typically takes 30 to 90 seconds and can reduce the file to 40-60% of its original size. You will see no output on success; the command returns silently to the prompt.

If sqlite3 is not installed, install the Xcode Command Line Tools with xcode-select --install, then retry.

Step 4: Use the Built-in "Reset Outlook" Option (Nuclear Option)

If performance is still poor after steps 1-3, or if Outlook is corrupted, Microsoft provides a full profile reset. This deletes all locally cached data and forces a fresh sync from the server. Use this only if you have Exchange or IMAP mail (all mail lives on the server) and you do not rely on local-only folders.

1. Hold Option and click the Outlook icon in the Dock (or Launchpad) to open the Microsoft Database Utility, if your version includes it. In newer builds of New Outlook, this utility has been removed.
2. For New Outlook (2024+), go to Help > Troubleshooting > Reset Outlook in the menu bar. This option wipes the local database and re-syncs from the server.
3. Alternatively, manually delete the entire profile folder at ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile/ while Outlook is closed. Outlook will recreate it and prompt you to add an account on next launch.

How Much Space Can You Expect to Recover?

Results vary by mailbox size and how long Outlook has been running without a cache clear. As rough benchmarks:

• Cache folder: 2 to 15 GB is common for accounts syncing more than a year of mail.
• Standard Caches: typically 200 MB to 1 GB.
• Database VACUUM: frequently reclaims 1 to 5 GB on accounts older than two years.

After completing all steps, empty the Trash to actually free the space on disk.

Preventing Outlook from Growing Back

A few settings reduce ongoing cache growth:

• Limit sync window: In Outlook, go to Outlook > Settings > Accounts, select your account, and set "Download email for" to 3 months or 1 month. Outlook will stop caching older messages locally.
• Remove large shared mailboxes: Delegate or shared mailboxes that you rarely use contribute heavily to the cache. Remove them from the account list if they are not frequently needed.
• Archive old mail server-side: Use your Exchange or Microsoft 365 admin portal to move mail older than a year to an online archive. This keeps the primary mailbox smaller and reduces what Outlook syncs.
• Re-run VACUUM periodically: A quarterly Terminal VACUUM keeps the database compact. It takes under two minutes and requires no data loss.

Finding Outlook's Cache with Crumb

If you want to see exactly how much space each Outlook folder is consuming before deleting anything, Crumb's whole-disk map surfaces the Group Containers path and shows the size of the cache and profile database side by side. Because Crumb reads the folder tree on-device without sending data anywhere, you can inspect Outlook's footprint, confirm the size, and decide what to remove. This is especially useful if you have multiple Outlook profiles or if you want a second opinion before running a VACUUM on a large database.

The manual steps above work without any third-party tool. But if you find yourself clearing Outlook caches every few months alongside other app leftovers, having a disk map that highlights the heaviest folders saves the investigative work each time.