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

AI file extension

Adobe Illustrator File

Vector Image Files

ASF file extension

Advanced Systems Format File

Video Files

CER file extension

Internet Security Certificate

Web Files

CSV file extension

Comma Separated Values File

Data Files

CUE file extension

Cue Sheet File

Disk Image Files

DMP file extension

Windows Memory Dump

System Files

ICO file extension

Icon File

System Files

JAVA file extension

Java Source Code File

Developer Files

JSP file extension

Java Server Page

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MP3 file extension

MP3 Audio File

Audio Files

PRF file extension

Outlook Profile File

Settings Files

WMV file extension

Windows Media Video File

Video Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

3G2 file extension

3GPP2 Multimedia File

Video Files