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

AVI file extension

Audio Video Interleave File

Video Files

BAK file extension

Backup File

Backup Files

C file extension

C/C++ Source Code File

Developer Files

CAB file extension

Windows Cabinet File

System Files

CLASS file extension

Java Class File

Developer Files

COM file extension

DOS Command File

Executable Files

DRV file extension

Device Driver

System Files

GADGET file extension

Windows Gadget

Executable Files

HTM file extension

Hypertext Markup Language File

Web Files

IFF file extension

Interchange File Format

Audio Files

PART file extension

Partially Downloaded File

Misc Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

TAR file extension

Consolidated Unix File Archive

Data Files

TXT file extension

Plain Text File

Text Files

VCD file extension

Virtual CD

Disk Image Files