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

CLASS file extension

Java Class File

Developer Files

M4V file extension

iTunes Video File

Video Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

TORRENT file extension

BitTorrent File

Misc Files

DMP file extension

Windows Memory Dump

System Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CSR file extension

Certificate Signing Request File

Web Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

FNT file extension

Windows Font File

Font Files

ISO file extension

Disc Image File

Disk Image Files

DOC# file extension

Microsoft Word Document

Text Files

3G2 file extension

3GPP2 Multimedia File

Video Files

APP file extension

Mac OS X Application

Executable Files

M3U file extension

Media Playlist File

Audio Files

7Z file extension

7-Zip Compressed File

Compressed Files