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

OBJ file extension

Wavefront 3D Object File

3D Image Files

TOAST file extension

Toast Disc Image

Disk Image Files

ASP file extension

Active Server Page

Web Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

DAT file extension

Data File

Data Files

SQL file extension

Structured Query Language Data File

Database Files

DOC# file extension

Microsoft Word Document

Text Files

KMZ file extension

Google Earth Placemark File

GIS Files

BAK file extension

Backup File

Backup Files

CSR file extension

Certificate Signing Request File

Web Files

KEY file extension

Keynote Presentation

Data Files

SLN file extension

Visual Studio Solution File

Developer Files

FNT file extension

Windows Font File

Font Files

7Z file extension

7-Zip Compressed File

Compressed Files

TIFF file extension

Tagged Image File Format

Raster Image Files