There is only one file type that uses the .TAR.GZ extension:
Compressed Tarball File
A TAR.GZ file is a TAR archive compressed with the standard GNU zip (gzip) compression algorithm. It contains one or more compressed files and is commonly used on Unix operating systems to package files, programs, and installers.
NOTE: TAR.GZ files must first be decompressed and then expanded using a TAR utility. They include both .TAR and .GZ file types.
|Apple Archive Utility||Bundled|
|File Viewer for Android||Free+|
|File Viewer Plus||Free Trial|
|Smith Micro StuffIt Deluxe||Commercial|
|Smith Micro Stuffit Deluxe Mac||Commercial|
Updated: March 18, 2016