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

CER file extension

Internet Security Certificate

Web Files

COM file extension

DOS Command File

Executable Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

M4A file extension

MPEG-4 Audio File

Audio Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

MOBI file extension

Mobipocket eBook

eBook Files

PART file extension

Partially Downloaded File

Misc Files

PNG file extension

Portable Network Graphic

Raster Image Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

ROM file extension

N64 Game ROM File

Game Files

SAV file extension

Saved Game

Game Files

SWF file extension

Shockwave Flash Movie

Video Files

TEX file extension

LaTeX Source Document

Text Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files