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

ASPX file extension

Active Server Page Extended File

Web Files

CUE file extension

Cue Sheet File

Disk Image Files

DAT file extension

Data File

Data Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

HTM file extension

Hypertext Markup Language File

Web Files

INDD file extension

Adobe InDesign Document

Layout Files

ISO file extension

Disc Image File

Disk Image Files

MP3 file extension

MP3 Audio File

Audio Files

MPA file extension

MPEG-2 Audio File

Audio Files

MSI file extension

Windows Installer Package

Misc Files

PNG file extension

Portable Network Graphic

Raster Image Files

ROM file extension

N64 Game ROM File

Game Files

TIFF file extension

Tagged Image File Format

Raster Image Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

3G2 file extension

3GPP2 Multimedia File

Video Files