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

DAT file extension

Data File

Data Files

DTD file extension

Document Type Definition File

Developer Files

INI file extension

Windows Initialization File

Settings Files

M4V file extension

iTunes Video File

Video Files

MP4 file extension

MPEG-4 Video File

Video Files

OTF file extension

OpenType Font

Font Files

PAGES file extension

Pages Document

Text Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TEX file extension

LaTeX Source Document

Text Files

TGA file extension

Targa Graphic

Raster Image Files

TIFF file extension

Tagged Image File Format

Raster Image Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

3GP file extension

3GPP Multimedia File

Video Files