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

CBR file extension

Comic Book RAR Archive

Compressed Files

CLASS file extension

Java Class File

Developer Files

DTD file extension

Document Type Definition File

Developer Files

EXE file extension

Windows Executable File

Executable Files

GED file extension

GEDCOM Genealogy Data File

Data Files

M4A file extension

MPEG-4 Audio File

Audio Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

ODT file extension

OpenDocument Text Document

Text Files

PAGES file extension

Pages Document

Text Files

PRF file extension

Outlook Profile File

Settings Files

SDF file extension

Standard Data File

Data Files

TGA file extension

Targa Graphic

Raster Image Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

3G2 file extension

3GPP2 Multimedia File

Video Files

3GP file extension

3GPP Multimedia File

Video Files