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

CER file extension

Internet Security Certificate

Web Files

CGI file extension

Common Gateway Interface Script

Executable Files

CPL file extension

Windows Control Panel Item

System Files

CSR file extension

Certificate Signing Request File

Web Files

CSS file extension

Cascading Style Sheet

Web Files

DOC file extension

Microsoft Word Document

Text Files

FLV file extension

Flash Video File

Video Files

ICO file extension

Icon File

System Files

MPA file extension

MPEG-2 Audio File

Audio Files

PCT file extension

Picture File

Layout Files

PIF file extension

Program Information File

Executable Files

VCF file extension

vCard File

Data Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

ZIP file extension

Zipped File

Compressed Files