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

CRX file extension

Chrome Extension

Plugin Files

DAT file extension

Data File

Data Files

DLL file extension

Dynamic Link Library

System Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

IBOOKS file extension

Multi-Touch iBook

Data Files

MPA file extension

MPEG-2 Audio File

Audio Files

ODT file extension

OpenDocument Text Document

Text Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

TAR file extension

Consolidated Unix File Archive

Data Files

TXT file extension

Plain Text File

Text Files

WAV file extension

WAVE Audio File

Audio Files

WMV file extension

Windows Media Video File

Video Files

WSF file extension

Windows Script File

Executable Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files