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

APK file extension

Android Package File

Executable Files

APP file extension

Mac OS X Application

Executable Files

BAK file extension

Backup File

Backup Files

CFG file extension

Configuration File

Settings Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

FNT file extension

Windows Font File

Font Files

GED file extension

GEDCOM Genealogy Data File

Data Files

HTM file extension

Hypertext Markup Language File

Web Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JAR file extension

Java Archive File

Executable Files

LNK file extension

Windows File Shortcut

System Files

MDB file extension

Microsoft Access Database

Database Files

PART file extension

Partially Downloaded File

Misc Files

3DS file extension

3D Studio Scene

3D Image Files

3GP file extension

3GPP Multimedia File

Video Files