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

CGI file extension

Common Gateway Interface Script

Executable Files

RTF file extension

Rich Text Format File

Text Files

H file extension

C/C++/Objective-C Header File

Developer Files

PDF file extension

Portable Document Format File

Layout Files

TMP file extension

Temporary File

Backup Files

RA file extension

Real Audio File

Audio Files

KMZ file extension

Google Earth Placemark File

GIS Files

CFM file extension

ColdFusion Markup File

Web Files

M3U file extension

Media Playlist File

Audio Files

THM file extension

Thumbnail Image File

Raster Image Files

ASF file extension

Advanced Systems Format File

Video Files

XCODEPROJ file extension

Xcode Project

Developer Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

CPL file extension

Windows Control Panel Item

System Files

7Z file extension

7-Zip Compressed File

Compressed Files