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

BAK file extension

Backup File

Backup Files

H file extension

C/C++/Objective-C Header File

Developer Files

DB file extension

Database File

Database Files

DOC file extension

Microsoft Word Document

Text Files

RTF file extension

Rich Text Format File

Text Files

7Z file extension

7-Zip Compressed File

Compressed Files

RA file extension

Real Audio File

Audio Files

CER file extension

Internet Security Certificate

Web Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

M file extension

Objective-C Implementation File

Developer Files

ICO file extension

Icon File

System Files

LOG file extension

Log File

Text Files

DDS file extension

DirectDraw Surface

Raster Image Files

COM file extension

DOS Command File

Executable Files

DEB file extension

Debian Software Package

Compressed Files