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

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

CRX file extension

Chrome Extension

Plugin Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

DAT file extension

Data File

Data Files

PY file extension

Python Script

Developer Files

BAT file extension

DOS Batch File

Executable Files

APP file extension

Mac OS X Application

Executable Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

CS file extension

Visual C# Source Code File

Developer Files

ISO file extension

Disc Image File

Disk Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

YUV file extension

YUV Encoded Image File

Raster Image Files

TARGZ file extension

Compressed Tarball File

Compressed Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files