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

DMG file extension

Mac OS X Disk Image

Disk Image Files

SQL file extension

Structured Query Language Data File

Database Files

PHP file extension

PHP Source Code File

Web Files

DDS file extension

DirectDraw Surface

Raster Image Files

GADGET file extension

Windows Gadget

Executable Files

CER file extension

Internet Security Certificate

Web Files

HTML file extension

Hypertext Markup Language File

Web Files

CFG file extension

Configuration File

Settings Files

ACCDB file extension

Access 2007 Database File

Database Files

SLN file extension

Visual Studio Solution File

Developer Files

ZIPX file extension

Extended Zip File

Compressed Files

CBR file extension

Comic Book RAR Archive

Compressed Files

7Z file extension

7-Zip Compressed File

Compressed Files

AZW file extension

Amazon Kindle eBook File

eBook Files

EXE file extension

Windows Executable File

Executable Files