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

CSR file extension

Certificate Signing Request File

Web Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

GADGET file extension

Windows Gadget

Executable Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

JAR file extension

Java Archive File

Executable Files

JS file extension

JavaScript File

Web Files

JSP file extension

Java Server Page

Web Files

MPG file extension

MPEG Video File

Video Files

ODT file extension

OpenDocument Text Document

Text Files

PDF file extension

Portable Document Format File

Layout Files

RA file extension

Real Audio File

Audio Files

SWF file extension

Shockwave Flash Movie

Video Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files