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

CGI file extension

Common Gateway Interface Script

Executable Files

CUR file extension

Windows Cursor

System Files

EPUB file extension

Open eBook File

eBook Files

JPG file extension

JPEG Image

Raster Image Files

KEY file extension

Keynote Presentation

Data Files

M file extension

Objective-C Implementation File

Developer Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

NES file extension

Nintendo (NES) ROM File

Game Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

TTF file extension

TrueType Font

Font Files

UUE file extension

Uuencoded File

Encoded Files

WAV file extension

WAVE Audio File

Audio Files

XML file extension

XML File

Data Files

ZIPX file extension

Extended Zip File

Compressed Files

3GP file extension

3GPP Multimedia File

Video Files