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

APP file extension

Mac OS X Application

Executable Files

CUE file extension

Cue Sheet File

Disk Image Files

DBF file extension

Database File

Database Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

JSP file extension

Java Server Page

Web Files

LOG file extension

Log File

Text Files

MDF file extension

Media Disc Image File

Disk Image Files

MOV file extension

Apple QuickTime Movie

Video Files

MSG file extension

Outlook Mail Message

Text Files

PDF file extension

Portable Document Format File

Layout Files

PPS file extension

PowerPoint Slide Show

Data Files

SAV file extension

Saved Game

Game Files

TGA file extension

Targa Graphic

Raster Image Files

ZIPX file extension

Extended Zip File

Compressed Files