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

TAR file extension

Consolidated Unix File Archive

Data Files

XCODEPROJ file extension

Xcode Project

Developer Files

VCD file extension

Virtual CD

Disk Image Files

ASPX file extension

Active Server Page Extended File

Web Files

PDF file extension

Portable Document Format File

Layout Files

BAT file extension

DOS Batch File

Executable Files

ZIP file extension

Zipped File

Compressed Files

TXT file extension

Plain Text File

Text Files

MOBI file extension

Mobipocket eBook

eBook Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

CPL file extension

Windows Control Panel Item

System Files

TIF file extension

Tagged Image File

Raster Image Files

KEY file extension

Keynote Presentation

Data Files

ICS file extension

iCalendar File

Misc Files

7Z file extension

7-Zip Compressed File

Compressed Files