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

ISO file extension

Disc Image File

Disk Image Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

3GP file extension

3GPP Multimedia File

Video Files

PY file extension

Python Script

Developer Files

DAT file extension

Data File

Data Files

CS file extension

Visual C# Source Code File

Developer Files

MOBI file extension

Mobipocket eBook

eBook Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

LNK file extension

Windows File Shortcut

System Files

TIFF file extension

Tagged Image File Format

Raster Image Files

APP file extension

Mac OS X Application

Executable Files

IBOOKS file extension

Multi-Touch iBook

Data Files

3DS file extension

3D Studio Scene

3D Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

CUR file extension

Windows Cursor

System Files