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

AI file extension

Adobe Illustrator File

Vector Image Files

ASF file extension

Advanced Systems Format File

Video Files

CUR file extension

Windows Cursor

System Files

DBF file extension

Database File

Database Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

EXE file extension

Windows Executable File

Executable Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

KMZ file extension

Google Earth Placemark File

GIS Files

M4A file extension

MPEG-4 Audio File

Audio Files

MP4 file extension

MPEG-4 Video File

Video Files

MSG file extension

Outlook Mail Message

Text Files

SH file extension

Bash Shell Script

Developer Files

THM file extension

Thumbnail Image File

Raster Image Files

TTF file extension

TrueType Font

Font Files

3DM file extension

Rhino 3D Model

3D Image Files