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

SRT file extension

SubRip Subtitle File

Video Files

CSR file extension

Certificate Signing Request File

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files

SQL file extension

Structured Query Language Data File

Database Files

BAK file extension

Backup File

Backup Files

TMP file extension

Temporary File

Backup Files

CSS file extension

Cascading Style Sheet

Web Files

FON file extension

Generic Font File

Font Files

JSP file extension

Java Server Page

Web Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

RA file extension

Real Audio File

Audio Files

CFM file extension

ColdFusion Markup File

Web Files

M4V file extension

iTunes Video File

Video Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

PCT file extension

Picture File

Layout Files