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

HTM file extension

Hypertext Markup Language File

Web Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

DDS file extension

DirectDraw Surface

Raster Image Files

DEB file extension

Debian Software Package

Compressed Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

PIF file extension

Program Information File

Executable Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

SRT file extension

SubRip Subtitle File

Video Files

IBOOKS file extension

Multi-Touch iBook

Data Files

DBF file extension

Database File

Database Files

7Z file extension

7-Zip Compressed File

Compressed Files

CFM file extension

ColdFusion Markup File

Web Files

LOG file extension

Log File

Text Files

PAGES file extension

Pages Document

Text Files