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

ASP file extension

Active Server Page

Web Files

CER file extension

Internet Security Certificate

Web Files

CLASS file extension

Java Class File

Developer Files

CPP file extension

C++ Source Code File

Developer Files

DOC# file extension

Microsoft Word Document

Text Files

DRV file extension

Device Driver

System Files

ICS file extension

iCalendar File

Misc Files

JS file extension

JavaScript File

Web Files

PDF file extension

Portable Document Format File

Layout Files

PL file extension

Perl Script

Developer Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TEX file extension

LaTeX Source Document

Text Files

TMP file extension

Temporary File

Backup Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

3G2 file extension

3GPP2 Multimedia File

Video Files