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

CPP file extension

C++ Source Code File

Developer Files

CSR file extension

Certificate Signing Request File

Web Files

LNK file extension

Windows File Shortcut

System Files

M4A file extension

MPEG-4 Audio File

Audio Files

MDF file extension

Media Disc Image File

Disk Image Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PCT file extension

Picture File

Layout Files

PNG file extension

Portable Network Graphic

Raster Image Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

SITX file extension

StuffIt X Archive

Compressed Files

SYS file extension

Windows System File

System Files

TARGZ file extension

Compressed Tarball File

Compressed Files

TMP file extension

Temporary File

Backup Files

TORRENT file extension

BitTorrent File

Misc Files

XLR file extension

Works Spreadsheet

Spreadsheet Files