Help determining the file type

To determine the file type is a simple two step process:

Determine the file extension.
Lookup the file type from the file extension.

Step 1. Determine the file extension

The file extension is the last part of a file name and is everthing after the dot. There is an FAQ article devoted to this topic: Help determining the file extension.

Step 2. Lookup the file type from the file extension

Once you know the file extension simply look that file extension up in the list of file extensions. This will either take you directly to the file type or it will take you to a list of possible file types.

Some file extensions are only used by one file type, so it is easy to determine the file type from the extension. Many other file extensions are claimed by more than one application, and where this happens you will be presented with a list of possible file types for that file extension.

When you have a list of possible file types, you can normally work out which is the correct file type by considering what you already know about the file. For example:

Why do you have the file? For example, consider if you have a file with the extension ".pdf" which someone has sent you and asked you to review, now a .pdf file could be a printer description file or it could be a portable document file. If you worked for a printer manufacturer then the file might reasonably be a printer description file, but otherwise it would almost certainly be a portable document file (PDF) which is a common format for exchanging human readable documents.
Is there an application already associated with the file? Just because there is an association between the file and an application does not mean that that application is necessarily the right application to open the file with, but it normally is.

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