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

ASPX file extension

Active Server Page Extended File

Web Files

BAK file extension

Backup File

Backup Files

BIN file extension

Binary Disc Image

Disk Image Files

CAB file extension

Windows Cabinet File

System Files

DAT file extension

Data File

Data Files

GZ file extension

Gnu Zipped Archive

Compressed Files

H file extension

C/C++/Objective-C Header File

Developer Files

INDD file extension

Adobe InDesign Document

Layout Files

MP3 file extension

MP3 Audio File

Audio Files

MSI file extension

Windows Installer Package

Misc Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

SYS file extension

Windows System File

System Files

TIFF file extension

Tagged Image File Format

Raster Image Files

TTF file extension

TrueType Font

Font Files

VOB file extension

DVD Video Object File

Video Files