Robin Williams Mac OS X Book, Jaguar Edition, The

Naming Your Files and Extensions

Below is a list of some (not all) common file extensions you might run across.

In Mac OS X, every file name has an extension (whether you see it or not), which is a short abbreviation at the end of a file name, preceded by a period, such as .jpg. This extension tells the Mac what to do with the file.

You can add your own extension to the end of a file name, if you know the exact characters for your document, or you can just let the Mac add the correct one for you; what you don’t want to do is add an extension without knowing that the Mac has added an extension to your extension. To make sure that doesn’t happen, or to make sure you get the extension you want, you can choose to see the extensions on a file-by-file ...