# Mac files--\>PC. Need file extensions! **URL:** \ **Category:** Factual Questions\ **Created:** [May 24, 2005, 6:24pm UTC](https://boards.straightdope.com/t/mac-files-pc-need-file-extensions/305299 "2005-05-24T18:24:28Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![StephenH](https://avatars.discourse-cdn.com/v4/letter/s/aca169/32.png) [@StephenH](https://boards.straightdope.com/u/StephenH)\ **Post date:** [May 24, 2005, 6:24pm UTC](https://boards.straightdope.com/t/mac-files-pc-need-file-extensions/305299/1 "2005-05-24T18:24:28Z")
Background: My wife used to own a mac running Mac OS 10.3. Its old and slow, and she needed a new Windows XP laptop for grad school so we bought one. However, when I transfered the files from her mac to the laptop I realized that the files were missing file extensions (they never had them to begin with). Currently the data files are on both her mac and her laptop. Problem: Hundreds of data files of multiple formats in dozens of folders need the proper extensions so they can be easily opened. Question: I assume the Mac knows what kind of file each one is… so I was wondering if there is some way for the mac to put all of the file extensions on all of the files. Can the OS do this? Is there a program to do this? Help me! (PS. No, the file extensions are not just hidden, they are non existent.) ---
**Author:** ![Beadalin](https://avatars.discourse-cdn.com/v4/letter/b/3be4f8/32.png) [@Beadalin](https://boards.straightdope.com/u/Beadalin)\ **Post date:** [May 24, 2005, 6:28pm UTC](https://boards.straightdope.com/t/mac-files-pc-need-file-extensions/305299/2 "2005-05-24T18:28:29Z")
If you are able to first group your files by filetype, something like a batch renaming program could help you out. [Here’s an example of one.](http://www.publicspace.net/ABetterFinderRename/) Using this or something like it, put all your Word documents (for example) into one folder and then run the batch rename to add the file extensions to each file.