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

APK file extension

Android Package File

Executable Files

APP file extension

Mac OS X Application

Executable Files

BMP file extension

Bitmap Image File

Raster Image Files

CSR file extension

Certificate Signing Request File

Web Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

DOC file extension

Microsoft Word Document

Text Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

GAM file extension

Saved Game File

Game Files

MPG file extension

MPEG Video File

Video Files

OTF file extension

OpenType Font

Font Files

PAGES file extension

Pages Document

Text Files

SAV file extension

Saved Game

Game Files

TARGZ file extension

Compressed Tarball File

Compressed Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

3DS file extension

3D Studio Scene

3D Image Files