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

BAK file extension

Backup File

Backup Files

CGI file extension

Common Gateway Interface Script

Executable Files

DBF file extension

Database File

Database Files

FLA file extension

Adobe Flash Animation

Developer Files

GPX file extension

GPS Exchange File

GIS Files

H file extension

C/C++/Objective-C Header File

Developer Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

M file extension

Objective-C Implementation File

Developer Files

PCT file extension

Picture File

Layout Files

PNG file extension

Portable Network Graphic

Raster Image Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RA file extension

Real Audio File

Audio Files

SDF file extension

Standard Data File

Data Files

SITX file extension

StuffIt X Archive

Compressed Files

YUV file extension

YUV Encoded Image File

Raster Image Files