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

BAK file extension

Backup File

Backup Files

CAB file extension

Windows Cabinet File

System Files

DEB file extension

Debian Software Package

Compressed Files

DOC file extension

Microsoft Word Document

Text Files

ICS file extension

iCalendar File

Misc Files

INI file extension

Windows Initialization File

Settings Files

JS file extension

JavaScript File

Web Files

M file extension

Objective-C Implementation File

Developer Files

MDF file extension

Media Disc Image File

Disk Image Files

MID file extension

MIDI File

Audio Files

MOBI file extension

Mobipocket eBook

eBook Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

SRT file extension

SubRip Subtitle File

Video Files

WSF file extension

Windows Script File

Executable Files

XLR file extension

Works Spreadsheet

Spreadsheet Files