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

APP file extension

Mac OS X Application
Executable Files

CLASS file extension

Java Class File
Developer Files

EXE file extension

Windows Executable File
Executable Files

GADGET file extension

Windows Gadget
Executable Files

ICO file extension

Icon File
System Files

KEYCHAIN file extension

Mac OS X Keychain File
Data Files

LOG file extension

Log File
Text Files

MIM file extension

Multi-Purpose Internet Mail Message File
Encoded Files

MOV file extension

Apple QuickTime Movie
Video Files

RPM file extension

Red Hat Package Manager File
Compressed Files

UUE file extension

Uuencoded File
Encoded Files

WPS file extension

Microsoft Works Word Processor Document
Text Files

XLR file extension

Works Spreadsheet
Spreadsheet Files

ZIPX file extension

Extended Zip File
Compressed Files