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

AVI file extension

Audio Video Interleave File

Video Files

DBF file extension

Database File

Database Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LNK file extension

Windows File Shortcut

System Files

M4V file extension

iTunes Video File

Video Files

OTF file extension

OpenType Font

Font Files

PDB file extension

Program Database

Database Files

PIF file extension

Program Information File

Executable Files

RPM file extension

Red Hat Package Manager File

Compressed Files

SH file extension

Bash Shell Script

Developer Files

SITX file extension

StuffIt X Archive

Compressed Files

TTF file extension

TrueType Font

Font Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

ZIP file extension

Zipped File

Compressed Files

3DM file extension

Rhino 3D Model

3D Image Files