File extensions – definition and basic information


File extensions are the integral parts of the files that are on each computer. Often, when working on a computer, we encounter a wide range of files, such as docx, ppt, part, mp3 or rmvb. We realize that they are there – but we often do not know what they are for on our computer.

File extension, also known as the filename extension is a suffix added to the name of a computer file, usually consisting of a number of characters placed after the last dot in the filename, which gives us information about its coding. In other words a file extension is a file format. It allows the operating system (e.g. Windows) to recognize what program it should try to open the file.

In the table below you will find a random selection of popular file extensions.


File extension The full name of the file Category

APP file extension

Mac OS X Application

Executable Files

PL file extension

Perl Script

Developer Files

EXE file extension

Windows Executable File

Executable Files

EPUB file extension

Open eBook File

eBook Files

TXT file extension

Plain Text File

Text Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

KML file extension

Keyhole Markup Language File

GIS Files

PDF file extension

Portable Document Format File

Layout Files

AIF file extension

Audio Interchange File Format

Audio Files

BAK file extension

Backup File

Backup Files

H file extension

C/C++/Objective-C Header File

Developer Files

CSV file extension

Comma Separated Values File

Data Files

7Z file extension

7-Zip Compressed File

Compressed Files

PDB file extension

Program Database

Database Files

DTD file extension

Document Type Definition File

Developer Files