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

BIN file extension

Binary Disc Image

Disk Image Files

CER file extension

Internet Security Certificate

Web Files

DLL file extension

Dynamic Link Library

System Files

DNG file extension

Digital Negative Image File

Camera Raw Files

H file extension

C/C++/Objective-C Header File

Developer Files

ICNS file extension

Mac OS X Icon Resource File

System Files

ICS file extension

iCalendar File

Misc Files

JAR file extension

Java Archive File

Executable Files

MDF file extension

Media Disc Image File

Disk Image Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PCT file extension

Picture File

Layout Files

PL file extension

Perl Script

Developer Files

TARGZ file extension

Compressed Tarball File

Compressed Files

TMP file extension

Temporary File

Backup Files

WPD file extension

WordPerfect Document

Text Files