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

APK file extension

Android Package File

Executable Files

CPP file extension

C++ Source Code File

Developer Files

DB file extension

Database File

Database Files

DOC# file extension

Microsoft Word Document

Text Files

DTD file extension

Document Type Definition File

Developer Files

EXE file extension

Windows Executable File

Executable Files

FNT file extension

Windows Font File

Font Files

ICS file extension

iCalendar File

Misc Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MDB file extension

Microsoft Access Database

Database Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

XCODEPROJ file extension

Xcode Project

Developer Files

ZIPX file extension

Extended Zip File

Compressed Files

3G2 file extension

3GPP2 Multimedia File

Video Files