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

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

IBOOKS file extension

Multi-Touch iBook

Data Files

THM file extension

Thumbnail Image File

Raster Image Files

SDF file extension

Standard Data File

Data Files

DMP file extension

Windows Memory Dump

System Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

SWF file extension

Shockwave Flash Movie

Video Files

DTD file extension

Document Type Definition File

Developer Files

PART file extension

Partially Downloaded File

Misc Files

TXT file extension

Plain Text File

Text Files

7Z file extension

7-Zip Compressed File

Compressed Files

AI file extension

Adobe Illustrator File

Vector Image Files

PY file extension

Python Script

Developer Files

JAVA file extension

Java Source Code File

Developer Files

VOB file extension

DVD Video Object File

Video Files