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

CSR file extension

Certificate Signing Request File

Web Files

DOC# file extension

Microsoft Word Document

Text Files

HTM file extension

Hypertext Markup Language File

Web Files

KEY file extension

Keynote Presentation

Data Files

MP3 file extension

MP3 Audio File

Audio Files

NES file extension

Nintendo (NES) ROM File

Game Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PCT file extension

Picture File

Layout Files

RPM file extension

Red Hat Package Manager File

Compressed Files

TGA file extension

Targa Graphic

Raster Image Files

THM file extension

Thumbnail Image File

Raster Image Files

TIFF file extension

Tagged Image File Format

Raster Image Files

WAV file extension

WAVE Audio File

Audio Files

ZIPX file extension

Extended Zip File

Compressed Files