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

AIF file extension

Audio Interchange File Format

Audio Files

CER file extension

Internet Security Certificate

Web Files

CSR file extension

Certificate Signing Request File

Web Files

GED file extension

GEDCOM Genealogy Data File

Data Files

HTM file extension

Hypertext Markup Language File

Web Files

IFF file extension

Interchange File Format

Audio Files

JAVA file extension

Java Source Code File

Developer Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

M file extension

Objective-C Implementation File

Developer Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

RA file extension

Real Audio File

Audio Files

SH file extension

Bash Shell Script

Developer Files

TIF file extension

Tagged Image File

Raster Image Files

WPD file extension

WordPerfect Document

Text Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files