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

AZW file extension

Amazon Kindle eBook File

eBook Files

CER file extension

Internet Security Certificate

Web Files

CFG file extension

Configuration File

Settings Files

CGI file extension

Common Gateway Interface Script

Executable Files

CSR file extension

Certificate Signing Request File

Web Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

NES file extension

Nintendo (NES) ROM File

Game Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

ROM file extension

N64 Game ROM File

Game Files

RTF file extension

Rich Text Format File

Text Files

VCD file extension

Virtual CD

Disk Image Files

VCF file extension

vCard File

Data Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files