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

SWF file extension

Shockwave Flash Movie

Video Files

KEY file extension

Keynote Presentation

Data Files

CGI file extension

Common Gateway Interface Script

Executable Files

7Z file extension

7-Zip Compressed File

Compressed Files

MP4 file extension

MPEG-4 Video File

Video Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

EPUB file extension

Open eBook File

eBook Files

APP file extension

Mac OS X Application

Executable Files

WAV file extension

WAVE Audio File

Audio Files

PPS file extension

PowerPoint Slide Show

Data Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

CUR file extension

Windows Cursor

System Files

INI file extension

Windows Initialization File

Settings Files

XCODEPROJ file extension

Xcode Project

Developer Files

3G2 file extension

3GPP2 Multimedia File

Video Files