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

CSV file extension

Comma Separated Values File

Data Files

DMP file extension

Windows Memory Dump

System Files

EXE file extension

Windows Executable File

Executable Files

GADGET file extension

Windows Gadget

Executable Files

ISO file extension

Disc Image File

Disk Image Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

OTF file extension

OpenType Font

Font Files

PDF file extension

Portable Document Format File

Layout Files

PL file extension

Perl Script

Developer Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

VOB file extension

DVD Video Object File

Video Files

WPD file extension

WordPerfect Document

Text Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

3DM file extension

Rhino 3D Model

3D Image Files