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

ASF file extension

Advanced Systems Format File

Video Files

AVI file extension

Audio Video Interleave File

Video Files

BAT file extension

DOS Batch File

Executable Files

CBR file extension

Comic Book RAR Archive

Compressed Files

CSR file extension

Certificate Signing Request File

Web Files

DTD file extension

Document Type Definition File

Developer Files

IBOOKS file extension

Multi-Touch iBook

Data Files

LOG file extension

Log File

Text Files

M4V file extension

iTunes Video File

Video Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PRF file extension

Outlook Profile File

Settings Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

SDF file extension

Standard Data File

Data Files

SYS file extension

Windows System File

System Files

3G2 file extension

3GPP2 Multimedia File

Video Files