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

DDS file extension

DirectDraw Surface

Raster Image Files

PIF file extension

Program Information File

Executable Files

CER file extension

Internet Security Certificate

Web Files

COM file extension

DOS Command File

Executable Files

WPD file extension

WordPerfect Document

Text Files

SWF file extension

Shockwave Flash Movie

Video Files

UUE file extension

Uuencoded File

Encoded Files

CAB file extension

Windows Cabinet File

System Files

GED file extension

GEDCOM Genealogy Data File

Data Files

LOG file extension

Log File

Text Files

ODT file extension

OpenDocument Text Document

Text Files

OTF file extension

OpenType Font

Font Files

MDB file extension

Microsoft Access Database

Database Files

7Z file extension

7-Zip Compressed File

Compressed Files

CS file extension

Visual C# Source Code File

Developer Files