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

BAK file extension

Backup File

Backup Files

PHP file extension

PHP Source Code File

Web Files

GED file extension

GEDCOM Genealogy Data File

Data Files

7Z file extension

7-Zip Compressed File

Compressed Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

CLASS file extension

Java Class File

Developer Files

AI file extension

Adobe Illustrator File

Vector Image Files

TIF file extension

Tagged Image File

Raster Image Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

TXT file extension

Plain Text File

Text Files

ICS file extension

iCalendar File

Misc Files

SQL file extension

Structured Query Language Data File

Database Files

LOG file extension

Log File

Text Files

JS file extension

JavaScript File

Web Files

ASP file extension

Active Server Page

Web Files