There is only one file type that uses the .UUD extension:
Decoded file that has been converted back to its original binary form; originally encoded by Unix UUEncode (into a .UUE file), which converts binary data into a text format.
Text encoding (UUEncoding) keeps files from being corrupted when being transferred over the Internet, but they must be decoded in order to be opened.
NOTE: The file extension may need to be changed from ".uud" to the original extension in order for the file to open correctly.
Updated: March 1, 2009