File Formats and Filename Extensions
When downloading files from the Internet, you will probably come across a wide variety of file formats, all of which can be identified by the file extension (a dot, normally followed by 2 to 4 letters or numbers). It is important to know what the format of the file is for a number of reasons:
- so that you know whether it will work on your computer
- so that you know whether you will need a particular type of software to decompress, play, or view it
It is also essential to check that the file has the right type of extension that you expect it to have; a file with an unknown or unexpected extension may in fact be a Trojan horse, which could seriously damage your system or others.
In this section, we take an in-depth look at file formats, along with a handy reference to file extensions by file type and in A-Z form.
