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

ICNS file extension

Mac OS X Icon Resource File

System Files

ISO file extension

Disc Image File

Disk Image Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

7Z file extension

7-Zip Compressed File

Compressed Files

XML file extension

XML File

Data Files

ASPX file extension

Active Server Page Extended File

Web Files

MP4 file extension

MPEG-4 Video File

Video Files

BMP file extension

Bitmap Image File

Raster Image Files

VCF file extension

vCard File

Data Files

COM file extension

DOS Command File

Executable Files

AVI file extension

Audio Video Interleave File

Video Files

SLN file extension

Visual Studio Solution File

Developer Files

PDF file extension

Portable Document Format File

Layout Files

MOBI file extension

Mobipocket eBook

eBook Files

CSS file extension

Cascading Style Sheet

Web Files