FileTypeDiag Dumps Complete File Type Association Information

FileTypeDiag is a useful tool that exports the complete file association information of a specified file type to a log file. Check out FileTypeDiag from, the same site which released a popular fix for the Adobe PDF thumbnails issue.

This tool can be helpful in troubleshooting cases such as:

  • Files don’t open when double-clicked, or open in the wrong application.
  • An incorrect icon is shown for a file type, although the file association is correct.
  • Clicking a media file causes explorer to crash. You need to investigate shell extensions for that file type.
  • Thumbnails or video previews (preview pane) are not generated.
  • An unwanted entry appears in the right-click menu for a particular file type that you want to remove.
  • Programs missing from Default Programs or Default Apps,
  • and other obscure problems.

FileTypeDiag Utility

filetypediagFileTypeDiag generates complete file association information for the file extension you specify. File type associations can be a complicated thing for many, but this tool makes everything easy by listing out all the file class data and also the Default Programs registration details for troubleshooting.

In the FileTypeDiag window, type the file extension which you want to investigate and click Save. The output is saved to a text file.

Tip: To output the “Folder”, “Directory”, and “Drive” association information, leave the “File extension” text box blank, and click Save…


If you’re not sure what exactly to look for in the text file, zip the file and send it to someone who can interpret the entries.

Editor’s note: I created a similar utility named FileExtInfo several years back, and haven’t had the chance to update it for the latest versions of Windows. Although it just runs fine even in Windows 10 but doesn’t enumerate entries in the 32-bit node in Windows 64-bit systems.

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Ramesh Srinivasan is passionate about Microsoft technologies and he has been a consecutive ten-time recipient of the Microsoft Most Valuable Professional award in the Windows Shell/Desktop Experience category, from 2003 to 2012. He loves to troubleshoot and write about Windows. Ramesh founded in 2005.

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