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

ASP file extension

Active Server Page

Web Files

BMP file extension

Bitmap Image File

Raster Image Files

CLASS file extension

Java Class File

Developer Files

CSR file extension

Certificate Signing Request File

Web Files

CSV file extension

Comma Separated Values File

Data Files

EXE file extension

Windows Executable File

Executable Files

GAM file extension

Saved Game File

Game Files

MOBI file extension

Mobipocket eBook

eBook Files

MSG file extension

Outlook Mail Message

Text Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

ODT file extension

OpenDocument Text Document

Text Files

PDB file extension

Program Database

Database Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RM file extension

Real Media File

Video Files

VOB file extension

DVD Video Object File

Video Files