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

MP4 file extension

MPEG-4 Video File

Video Files

7Z file extension

7-Zip Compressed File

Compressed Files

DOC file extension

Microsoft Word Document

Text Files

TAR file extension

Consolidated Unix File Archive

Data Files

SQL file extension

Structured Query Language Data File

Database Files

VOB file extension

DVD Video Object File

Video Files

SITX file extension

StuffIt X Archive

Compressed Files

BAK file extension

Backup File

Backup Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

DAT file extension

Data File

Data Files

MPA file extension

MPEG-2 Audio File

Audio Files

M file extension

Objective-C Implementation File

Developer Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

CGI file extension

Common Gateway Interface Script

Executable Files

NES file extension

Nintendo (NES) ROM File

Game Files