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

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

MP3 file extension

MP3 Audio File

Audio Files

DBF file extension

Database File

Database Files

FLV file extension

Flash Video File

Video Files

3G2 file extension

3GPP2 Multimedia File

Video Files

KEY file extension

Keynote Presentation

Data Files

TMP file extension

Temporary File

Backup Files

HTM file extension

Hypertext Markup Language File

Web Files

VOB file extension

DVD Video Object File

Video Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

ZIPX file extension

Extended Zip File

Compressed Files

TIFF file extension

Tagged Image File Format

Raster Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

MSG file extension

Outlook Mail Message

Text Files

DWG file extension

AutoCAD Drawing Database File

CAD Files