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

AI file extension

Adobe Illustrator File

Vector Image Files

ASPX file extension

Active Server Page Extended File

Web Files

BAK file extension

Backup File

Backup Files

CAB file extension

Windows Cabinet File

System Files

DOC# file extension

Microsoft Word Document

Text Files

GED file extension

GEDCOM Genealogy Data File

Data Files

M file extension

Objective-C Implementation File

Developer Files

M4V file extension

iTunes Video File

Video Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PRF file extension

Outlook Profile File

Settings Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TORRENT file extension

BitTorrent File

Misc Files

WAV file extension

WAVE Audio File

Audio Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files