Outlook stores temporary files to let you preview attachments without opening them. This cache can fill up over time, causing slow performance and errors. The issue occurs because the temporary files folder is not automatically cleaned. This article explains how to locate and clear the Outlook attachment preview cache.
Key Takeaways: Clearing the Attachment Preview Cache
- File > Options > Trust Center > Trust Center Settings > Attachment Handling: Disables the previewer to allow safe deletion of cached files.
- Windows Run dialog (Win + R) and %temp% command: Opens the main Windows temporary files folder for manual cleanup.
- Outlook Secure Temp Folder path: The specific location where Outlook stores attachment preview data, separate from the main temp folder.
How Outlook’s Attachment Preview Cache Works
Outlook uses a feature called the Preview Pane to show the contents of attachments like PDFs or images. To display these files quickly, it creates temporary cached copies in a secure folder on your computer. This process happens automatically when you select an email with an attachment.
The cache is designed to be isolated for security, preventing malicious files from affecting your system. However, Outlook does not regularly delete these cached files. Over weeks or months, the folder can accumulate hundreds of megabytes of data. A full cache can slow down the preview feature, cause Outlook to freeze, or trigger low disk space warnings.
Locations of Temporary Files
Outlook uses two primary locations for temporary data. The general Windows Temp folder (%temp%) holds various application files. The Outlook Secure Temp Folder is dedicated solely to attachment previews. You need to clear files from both locations for a complete cleanup. The Secure Temp Folder path is often hidden within your user AppData directory.
Steps to Clear the Outlook Attachment Preview Cache
Follow these steps to safely delete the cached temporary files. Start by closing Outlook completely.
- Disable the attachment previewer in Outlook
Open Outlook and go to File > Options. Select Trust Center, then click the Trust Center Settings button. In the new window, choose Attachment Handling. Uncheck the box for Turn off attachment preview. Click OK twice to save and close the options windows. This step ensures Outlook is not using the cached files when you delete them. - Open the Windows Temp folder
Press the Windows key + R to open the Run dialog. Type %temp% and press Enter. This command opens the main temporary files folder for your user account. Do not close this File Explorer window. - Delete files from the Windows Temp folder
In the opened folder, press Ctrl + A to select all items. Right-click on any selected file and choose Delete. You may see an error that some files are in use. Click Skip for those files. This action moves most temporary data to the Recycle Bin. - Navigate to the Outlook Secure Temp Folder
Open a new File Explorer window. Paste this exact path into the address bar and press Enter: %USERPROFILE%\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.Outlook\. You might need to enable Show hidden files in File Explorer View options to see this folder. - Clear the Outlook-specific cache
Inside the Content.Outlook folder, you will see several folders with random names. Select all these folders, right-click, and choose Delete. This removes the cached attachment preview data. Empty your Recycle Bin afterward to free up disk space. - Re-enable attachment preview
Reopen Outlook. Go back to File > Options > Trust Center > Trust Center Settings > Attachment Handling. Check the box for Turn off attachment preview to re-enable the feature. Click OK to confirm. The cache will start rebuilding as you preview new attachments.
Common Mistakes and Things to Avoid
Deleting Files While Outlook is Running
If Outlook is open, the temporary files may be locked by the system. Attempting to delete them will cause file-in-use errors. Always ensure Outlook is fully closed from the system tray before starting the cleanup process. Check Task Manager to confirm the Outlook.exe process is not running.
Clearing the Wrong Folder
The main Windows Temp folder and the Outlook Secure Temp Folder are different. Deleting only the general temp files will not clear the attachment preview cache. You must navigate to the specific Content.Outlook path to remove the correct data. Double-check the folder path in the address bar.
Not Emptying the Recycle Bin
Deleted temporary files remain in the Recycle Bin until you empty it. This means disk space is not immediately recovered. After following the steps, right-click the Recycle Bin icon on your desktop and select Empty Recycle Bin. Confirm the action to permanently remove the files.
Manual Cleanup vs. Disk Cleanup Tool
| Item | Manual Folder Deletion | Windows Disk Cleanup Tool |
|---|---|---|
| Targeted Cleanup | Specifically removes Outlook preview cache | Cleans broad system temp files and updates |
| Speed | Fast, direct access to the problem folder | Slower, requires scanning the entire drive |
| Effectiveness for Outlook | Guarantees the Outlook cache is cleared | May not clean the Secure Temp Folder |
| Skill Required | Requires knowledge of specific folder paths | Simple guided wizard interface |
| Risk Level | Low if correct folders are targeted | Very low, as it is a system tool |
You can now clear the Outlook attachment preview cache to fix performance issues. Regularly deleting these temporary files prevents the folder from filling up again. For a more automated approach, consider using the Windows Storage Sense feature to clean temp files. An advanced tip is to create a desktop shortcut to the Content.Outlook folder for quick future access.