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

BAK file extension

Backup File

Backup Files

CGI file extension

Common Gateway Interface Script

Executable Files

CSR file extension

Certificate Signing Request File

Web Files

DAT file extension

Data File

Data Files

DDS file extension

DirectDraw Surface

Raster Image Files

DXF file extension

Drawing Exchange Format File

CAD Files

IFF file extension

Interchange File Format

Audio Files

JS file extension

JavaScript File

Web Files

LUA file extension

Lua Source File

Developer Files

MOBI file extension

Mobipocket eBook

eBook Files

PDB file extension

Program Database

Database Files

RPM file extension

Red Hat Package Manager File

Compressed Files

TARGZ file extension

Compressed Tarball File

Compressed Files

VCF file extension

vCard File

Data Files

WSF file extension

Windows Script File

Executable Files