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

AZW file extension

Amazon Kindle eBook File

eBook Files

CFM file extension

ColdFusion Markup File

Web Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CUR file extension

Windows Cursor

System Files

DLL file extension

Dynamic Link Library

System Files

GED file extension

GEDCOM Genealogy Data File

Data Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

IBOOKS file extension

Multi-Touch iBook

Data Files

M4A file extension

MPEG-4 Audio File

Audio Files

MOV file extension

Apple QuickTime Movie

Video Files

PCT file extension

Picture File

Layout Files

PRF file extension

Outlook Profile File

Settings Files

SQL file extension

Structured Query Language Data File

Database Files

3G2 file extension

3GPP2 Multimedia File

Video Files