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

ASF file extension

Advanced Systems Format File

Video Files

CFG file extension

Configuration File

Settings Files

CFM file extension

ColdFusion Markup File

Web Files

CSR file extension

Certificate Signing Request File

Web Files

DDS file extension

DirectDraw Surface

Raster Image Files

DEB file extension

Debian Software Package

Compressed Files

EXE file extension

Windows Executable File

Executable Files

FLV file extension

Flash Video File

Video Files

MP3 file extension

MP3 Audio File

Audio Files

MP4 file extension

MPEG-4 Video File

Video Files

PNG file extension

Portable Network Graphic

Raster Image Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

PY file extension

Python Script

Developer Files

WMA file extension

Windows Media Audio File

Audio Files

WPS file extension

Microsoft Works Word Processor Document

Text Files