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

7Z file extension

7-Zip Compressed File

Compressed Files

APP file extension

Mac OS X Application

Executable Files

MOBI file extension

Mobipocket eBook

eBook Files

DNG file extension

Digital Negative Image File

Camera Raw Files

M file extension

Objective-C Implementation File

Developer Files

WSF file extension

Windows Script File

Executable Files

CUR file extension

Windows Cursor

System Files

3DS file extension

3D Studio Scene

3D Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

BMP file extension

Bitmap Image File

Raster Image Files

JAVA file extension

Java Source Code File

Developer Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

APK file extension

Android Package File

Executable Files

CGI file extension

Common Gateway Interface Script

Executable Files

PKG file extension

Mac OS X Installer Package

Compressed Files