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

BAT file extension

DOS Batch File

Executable Files

CAB file extension

Windows Cabinet File

System Files

CS file extension

Visual C# Source Code File

Developer Files

CSR file extension

Certificate Signing Request File

Web Files

DBF file extension

Database File

Database Files

EXE file extension

Windows Executable File

Executable Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

ICNS file extension

Mac OS X Icon Resource File

System Files

ICO file extension

Icon File

System Files

LOG file extension

Log File

Text Files

PDF file extension

Portable Document Format File

Layout Files

PL file extension

Perl Script

Developer Files

ROM file extension

N64 Game ROM File

Game Files

SDF file extension

Standard Data File

Data Files

WPD file extension

WordPerfect Document

Text Files