Do you keep getting the "this file cannot be previewed" error when previewing attachments in Outlook? The good news is that you don't need to download attachments every time you want to view them, as it is possible to fix this annoying issue.

Below, we share eight quick and easy fixes for resolving the “this file cannot be previewed” error in Outlook for Windows.

1. Install Relevant Apps to Preview Files

Outlook may fail to preview attachments if the appropriate app for the file format is not installed on your PC. For instance, if you don’t have a PDF reader app on your PC, Outlook may display the “this file cannot be previewed because there is no previewer installed for it” error.

To avoid this, ensure that the appropriate app or software for the file format is available on your computer. After that, Outlook should be able to preview your files without any problems.

2. Disable Preview Handler in PowerToys

Using Microsoft PowerToys is an excellent way to boost your productivity on Windows computers. However, these PowerToys utilities can sometimes interfere with app processes and prevent apps from working properly.

Several users on the forums reported fixing Outlook’s “this file cannot be previewed” error by disabling the Preview Handler feature. You can also give this method a shot.

  1. Open the PowerToys app using the search menu.
  2. Switch to the File Explorer add-ons tab using the left sidebar.
  3. Under the Preview Pane section, disable the toggle next to Portable Document Format.
    Disable Preview Handlers in PowerToys

3. Enable Attachment Preview in Outlook

It's possible that Outlook is failing to preview attachments because the file previewer feature is disabled in the app. To overrule this possibility, you need to check the attachment handling settings in Outlook.

  1. Open the Outlook app on your PC.
  2. Click the File menu in the top left corner.
  3. Select Options from the left sidebar.
  4. Navigate to the Trust Center tab and click the Trust Center Settings button.
  5. In the Attachment Handling tab, clear the Turn off Attachment Preview checkbox.
  6. Click on Attachment and Document Previewers and make sure all the previewers are active. Then, click OK.
  7. Restart the Outlook app after this and see if you can preview attachments.
    Attachment Handling in Outlook

4. Change Outlook User Interface Settings

Another thing you can do is tweak the User Interface Settings in Outlook and see if that gets the app to load attachment previews on Windows. Here are the steps for the same:

  1. Open the Outlook app and click the File menu at the top.
  2. Select Options from the left column.
  3. In the Outlook Options window, navigate to the General tab.
  4. Under the User Interface Settings section, select Optimize for compatibility option.
    Optimize Outlook for Compatibility

Restart the Outlook app after this and check if the issue is still there.

5. Clear Outlook Cache

Outlook, like most apps, stores cache files on your computer to reduce loading times. Although this data is supposed to improve app performance, it’s not uncommon for it to become corrupted over time. When this happens, Outlook may malfunction or throw strange errors. You can try deleting the Outlook cache and see if that helps.

To delete Outlook cache data on Windows, use these steps:

  1. Right-click on the Start icon or press Win + X to open the Power User menu.
  2. Select Run from the list.
  3. Type %localappdata%\Microsoft\Outlook in the text box and press Enter.
  4. In the RoamCache folder that appears, select all the files and click the trash icon at the top to delete them.
    Delete Outlook Cache Data

6. Enable Windows Firewall

Have you disabled Windows Defender Firewall on your computer? That could prevent Outlook from previewing attachments.

Here's how to check if the Windows Defender Firewall is enabled on your PC.

  1. Press Win + S to open the search menu.
  2. Type Windows Security in the search box and press Enter.
  3. Select Firewall & network protection tab from the left pane.
  4. Choose a network profile.
  5. Enable the toggle for Windows Defender Firewall.
    Enable Microsoft Defender Firewall

7. Modify Registry Files

Incorrect Windows Registry settings could also cause such anomalies. If that's the case, you'll need to correct the Registry settings manually on your PC.

Since Registry files contain important settings for Windows and its apps, you should only use this method if you’re familiar with editing Registry files. Also, it’s a good idea to back up all the Registry files before you proceed. If you need help with that, check our guide on how to back up Windows Registry and follow the steps outlined there.

  1. Press Win + R to open the Run dialog.
  2. Type regedit in the text box and press Enter.
  3. Select Yes when the User Account Control (UAC) prompt appears.
  4. Use the left pane to navigate to HKEY_LOCAL_MACHINE > ​SOFTWARE > ​Microsoft > ​Windows > ​CurrentVersion > ​PreviewHandlers.
  5. Look for the following string values and check the associated Data on the right side. 
            {00020827-0000-0000-C000-000000000046} = Microsoft Excel previewer
    {21E17C2F-AD3A-4b89-841F-09CFE02D16B7} = Microsoft Visio previewer
    {65235197-874B-4A07-BDC5-E65EA825B718} = Microsoft PowerPoint previewer
    {84F66100-FF7C-4fb4-B0C0-02CD7FB668FE} = Microsoft Word previewer
    {DC6EFB56-9CFA-464D-8880-44885D7DC193} = Adobe PDF Preview Handler for Vista
    Preview Handlers in Registry
  6. If any of the above-mentioned values are missing, right-click on an empty spot and select New > String Value.
  7. Double-click on the newly created string value.
  8. Enter the name of the application handler in the Value data field and click OK.
  9. Right-click on the string value, select Rename and type the value associated with the application handler.
  10. Exit the Registry Editor window and restart your PC.
    Edit String in Registry

8. Run the Microsoft Office Repair Tool

Microsoft Office includes a repair tool for fixing Office apps on Windows. So, if nothing works, you can run this tool to repair the Outlook app. Here's how:

  1. Use one of the many ways to open the Control Panel.
  2. Go to Programs and Features.
  3. Locate and select Microsoft Office on the list. Then, click the Change button at the top.
  4. Select Quick Repair and then click Repair.
    Repair Microsoft Office

Wait for the process to finish and check if you can preview files. If you can't, repeat the above steps to perform an Online Repair. As suggestive of its name, this process does necessitate an active internet connection on your computer.

Preview Your Outlook Attachments Again on Windows

One of these eight fixes should take care of the “this file cannot be previewed” error in Outlook. If not, you can consider reinstalling the Outlook app as a last resort.

If you're tired of dealing with the Outlook app's recurring problems, there are plenty of excellent email clients for Windows.