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

DDS file extension

DirectDraw Surface

Raster Image Files

3DM file extension

Rhino 3D Model

3D Image Files

SITX file extension

StuffIt X Archive

Compressed Files

FNT file extension

Windows Font File

Font Files

XML file extension

XML File

Data Files

MDB file extension

Microsoft Access Database

Database Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

7Z file extension

7-Zip Compressed File

Compressed Files

CGI file extension

Common Gateway Interface Script

Executable Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

TXT file extension

Plain Text File

Text Files

GPX file extension

GPS Exchange File

GIS Files

MSG file extension

Outlook Mail Message

Text Files

LOG file extension

Log File

Text Files

M4A file extension

MPEG-4 Audio File

Audio Files