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

PCT file extension

Picture File

Layout Files

TXT file extension

Plain Text File

Text Files

ASF file extension

Advanced Systems Format File

Video Files

ODT file extension

OpenDocument Text Document

Text Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

DOC file extension

Microsoft Word Document

Text Files

ICS file extension

iCalendar File

Misc Files

DNG file extension

Digital Negative Image File

Camera Raw Files

PART file extension

Partially Downloaded File

Misc Files

CFM file extension

ColdFusion Markup File

Web Files

JS file extension

JavaScript File

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files

TTF file extension

TrueType Font

Font Files

MP4 file extension

MPEG-4 Video File

Video Files

BIN file extension

Binary Disc Image

Disk Image Files