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

GZ file extension

Gnu Zipped Archive

Compressed Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

7Z file extension

7-Zip Compressed File

Compressed Files

HTML file extension

Hypertext Markup Language File

Web Files

VCXPROJ file extension

Visual C++ Project

Developer Files

LOG file extension

Log File

Text Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

CLASS file extension

Java Class File

Developer Files

ZIP file extension

Zipped File

Compressed Files

JPG file extension

JPEG Image

Raster Image Files

ICO file extension

Icon File

System Files

FON file extension

Generic Font File

Font Files

FNT file extension

Windows Font File

Font Files

ASF file extension

Advanced Systems Format File

Video Files

DLL file extension

Dynamic Link Library

System Files