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

GED file extension

GEDCOM Genealogy Data File

Data Files

CSR file extension

Certificate Signing Request File

Web Files

BAK file extension

Backup File

Backup Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

WPD file extension

WordPerfect Document

Text Files

CSV file extension

Comma Separated Values File

Data Files

SITX file extension

StuffIt X Archive

Compressed Files

7Z file extension

7-Zip Compressed File

Compressed Files

3GP file extension

3GPP Multimedia File

Video Files

GADGET file extension

Windows Gadget

Executable Files

THM file extension

Thumbnail Image File

Raster Image Files

APK file extension

Android Package File

Executable Files

SWF file extension

Shockwave Flash Movie

Video Files

CPP file extension

C++ Source Code File

Developer Files

DRV file extension

Device Driver

System Files