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

ACCDB file extension

Access 2007 Database File

Database Files

JS file extension

JavaScript File

Web Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

UUE file extension

Uuencoded File

Encoded Files

CS file extension

Visual C# Source Code File

Developer Files

LNK file extension

Windows File Shortcut

System Files

VCF file extension

vCard File

Data Files

SITX file extension

StuffIt X Archive

Compressed Files

7Z file extension

7-Zip Compressed File

Compressed Files

FNT file extension

Windows Font File

Font Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

ASP file extension

Active Server Page

Web Files

CSV file extension

Comma Separated Values File

Data Files

PKG file extension

Mac OS X Installer Package

Compressed Files

ISO file extension

Disc Image File

Disk Image Files