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

ASF file extension

Advanced Systems Format File

Video Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CS file extension

Visual C# Source Code File

Developer Files

DOC# file extension

Microsoft Word Document

Text Files

DTD file extension

Document Type Definition File

Developer Files

ICNS file extension

Mac OS X Icon Resource File

System Files

ICS file extension

iCalendar File

Misc Files

ISO file extension

Disc Image File

Disk Image Files

JPG file extension

JPEG Image

Raster Image Files

M4V file extension

iTunes Video File

Video Files

PPT file extension

PowerPoint Presentation

Data Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

SWF file extension

Shockwave Flash Movie

Video Files

TGA file extension

Targa Graphic

Raster Image Files

ZIPX file extension

Extended Zip File

Compressed Files