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

7Z file extension

7-Zip Compressed File

Compressed Files

DRV file extension

Device Driver

System Files

EPUB file extension

Open eBook File

eBook Files

BMP file extension

Bitmap Image File

Raster Image Files

INDD file extension

Adobe InDesign Document

Layout Files

SITX file extension

StuffIt X Archive

Compressed Files

3GP file extension

3GPP Multimedia File

Video Files

XCODEPROJ file extension

Xcode Project

Developer Files

DXF file extension

Drawing Exchange Format File

CAD Files

ASPX file extension

Active Server Page Extended File

Web Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

APP file extension

Mac OS X Application

Executable Files

MID file extension

MIDI File

Audio Files

RA file extension

Real Audio File

Audio Files

TXT file extension

Plain Text File

Text Files