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

TIFF file extension

Tagged Image File Format

Raster Image Files

BAK file extension

Backup File

Backup Files

PAGES file extension

Pages Document

Text Files

7Z file extension

7-Zip Compressed File

Compressed Files

LOG file extension

Log File

Text Files

CPL file extension

Windows Control Panel Item

System Files

3DS file extension

3D Studio Scene

3D Image Files

CSR file extension

Certificate Signing Request File

Web Files

KMZ file extension

Google Earth Placemark File

GIS Files

PKG file extension

Mac OS X Installer Package

Compressed Files

THM file extension

Thumbnail Image File

Raster Image Files

MDB file extension

Microsoft Access Database

Database Files

SQL file extension

Structured Query Language Data File

Database Files

RSS file extension

Rich Site Summary

Web Files

TAR file extension

Consolidated Unix File Archive

Data Files