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

LOG file extension

Log File

Text Files

FNT file extension

Windows Font File

Font Files

JAVA file extension

Java Source Code File

Developer Files

WMV file extension

Windows Media Video File

Video Files

RM file extension

Real Media File

Video Files

ICNS file extension

Mac OS X Icon Resource File

System Files

BAK file extension

Backup File

Backup Files

SRT file extension

SubRip Subtitle File

Video Files

7Z file extension

7-Zip Compressed File

Compressed Files

WPD file extension

WordPerfect Document

Text Files

GED file extension

GEDCOM Genealogy Data File

Data Files

MOBI file extension

Mobipocket eBook

eBook Files

ODT file extension

OpenDocument Text Document

Text Files

RPM file extension

Red Hat Package Manager File

Compressed Files

CPL file extension

Windows Control Panel Item

System Files