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

AVI file extension

Audio Video Interleave File

Video Files

CER file extension

Internet Security Certificate

Web Files

DB file extension

Database File

Database Files

DOC file extension

Microsoft Word Document

Text Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

FNT file extension

Windows Font File

Font Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

ICNS file extension

Mac OS X Icon Resource File

System Files

MOBI file extension

Mobipocket eBook

eBook Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

SH file extension

Bash Shell Script

Developer Files

TTF file extension

TrueType Font

Font Files

WSF file extension

Windows Script File

Executable Files