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

CBR file extension

Comic Book RAR Archive

Compressed Files

CSV file extension

Comma Separated Values File

Data Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

EPUB file extension

Open eBook File

eBook Files

JAVA file extension

Java Source Code File

Developer Files

JSP file extension

Java Server Page

Web Files

KMZ file extension

Google Earth Placemark File

GIS Files

MP4 file extension

MPEG-4 Video File

Video Files

PAGES file extension

Pages Document

Text Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

TGA file extension

Targa Graphic

Raster Image Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

3GP file extension

3GPP Multimedia File

Video Files