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

ASF file extension

Advanced Systems Format File

Video Files

CAB file extension

Windows Cabinet File

System Files

DB file extension

Database File

Database Files

DLL file extension

Dynamic Link Library

System Files

DRV file extension

Device Driver

System Files

ISO file extension

Disc Image File

Disk Image Files

LOG file extension

Log File

Text Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

SDF file extension

Standard Data File

Data Files

VCF file extension

vCard File

Data Files

WSF file extension

Windows Script File

Executable Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

3DM file extension

Rhino 3D Model

3D Image Files

3DS file extension

3D Studio Scene

3D Image Files

3G2 file extension

3GPP2 Multimedia File

Video Files