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

CER file extension

Internet Security Certificate

Web Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CS file extension

Visual C# Source Code File

Developer Files

DAT file extension

Data File

Data Files

DMP file extension

Windows Memory Dump

System Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MSI file extension

Windows Installer Package

Misc Files

ODT file extension

OpenDocument Text Document

Text Files

PIF file extension

Program Information File

Executable Files

PL file extension

Perl Script

Developer Files

RTF file extension

Rich Text Format File

Text Files

TEX file extension

LaTeX Source Document

Text Files

TXT file extension

Plain Text File

Text Files

3DS file extension

3D Studio Scene

3D Image Files