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

ACCDB file extension

Access 2007 Database File

Database Files

AI file extension

Adobe Illustrator File

Vector Image Files

C file extension

C/C++ Source Code File

Developer Files

CS file extension

Visual C# Source Code File

Developer Files

CSV file extension

Comma Separated Values File

Data Files

EXE file extension

Windows Executable File

Executable Files

PCT file extension

Picture File

Layout Files

PDB file extension

Program Database

Database 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

TMP file extension

Temporary File

Backup Files

UUE file extension

Uuencoded File

Encoded Files

WMV file extension

Windows Media Video File

Video Files

XCODEPROJ file extension

Xcode Project

Developer Files