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

CER file extension

Internet Security Certificate

Web Files

DLL file extension

Dynamic Link Library

System Files

DRV file extension

Device Driver

System Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

GBR file extension

Gerber File

Data Files

INI file extension

Windows Initialization File

Settings Files

LNK file extension

Windows File Shortcut

System Files

MID file extension

MIDI File

Audio Files

MSG file extension

Outlook Mail Message

Text Files

OTF file extension

OpenType Font

Font Files

PDF file extension

Portable Document Format File

Layout Files

PKG file extension

Mac OS X Installer Package

Compressed Files

TEX file extension

LaTeX Source Document

Text Files

VB file extension

VBScript File

Executable Files

XLR file extension

Works Spreadsheet

Spreadsheet Files