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

BAK file extension

Backup File

Backup Files

CSR file extension

Certificate Signing Request File

Web Files

DMP file extension

Windows Memory Dump

System Files

DRV file extension

Device Driver

System Files

DTD file extension

Document Type Definition File

Developer Files

GADGET file extension

Windows Gadget

Executable Files

ICS file extension

iCalendar File

Misc Files

PRF file extension

Outlook Profile File

Settings Files

PY file extension

Python Script

Developer Files

SITX file extension

StuffIt X Archive

Compressed Files

SRT file extension

SubRip Subtitle File

Video Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

VCXPROJ file extension

Visual C++ Project

Developer Files

ZIP file extension

Zipped File

Compressed Files

3DM file extension

Rhino 3D Model

3D Image Files