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

ASX file extension

Microsoft ASF Redirector File

Video Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

DXF file extension

Drawing Exchange Format File

CAD Files

GADGET file extension

Windows Gadget

Executable Files

LNK file extension

Windows File Shortcut

System Files

MAX file extension

3ds Max Scene File

3D Image Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RM file extension

Real Media File

Video Files

SQL file extension

Structured Query Language Data File

Database Files

THM file extension

Thumbnail Image File

Raster Image Files

TMP file extension

Temporary File

Backup Files

TTF file extension

TrueType Font

Font Files