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

ASPX file extension

Active Server Page Extended File

Web Files

C file extension

C/C++ Source Code File

Developer Files

CUE file extension

Cue Sheet File

Disk Image Files

GBR file extension

Gerber File

Data Files

HTML file extension

Hypertext Markup Language File

Web Files

INI file extension

Windows Initialization File

Settings Files

ISO file extension

Disc Image File

Disk Image Files

LUA file extension

Lua Source File

Developer Files

M4A file extension

MPEG-4 Audio File

Audio Files

MOBI file extension

Mobipocket eBook

eBook Files

PART file extension

Partially Downloaded File

Misc Files

TMP file extension

Temporary File

Backup Files

TXT file extension

Plain Text File

Text Files

XML file extension

XML File

Data Files

ZIPX file extension

Extended Zip File

Compressed Files