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

AVI file extension

Audio Video Interleave File

Video Files

AZW file extension

Amazon Kindle eBook File

eBook Files

CSR file extension

Certificate Signing Request File

Web Files

DMP file extension

Windows Memory Dump

System Files

INDD file extension

Adobe InDesign Document

Layout Files

LNK file extension

Windows File Shortcut

System Files

MP3 file extension

MP3 Audio File

Audio Files

MSG file extension

Outlook Mail Message

Text Files

PHP file extension

PHP Source Code File

Web Files

SDF file extension

Standard Data File

Data Files

SITX file extension

StuffIt X Archive

Compressed Files

SRT file extension

SubRip Subtitle File

Video Files

TGA file extension

Targa Graphic

Raster Image Files

TXT file extension

Plain Text File

Text Files

ZIP file extension

Zipped File

Compressed Files