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

PCT file extension

Picture File

Layout Files

7Z file extension

7-Zip Compressed File

Compressed Files

RTF file extension

Rich Text Format File

Text Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

DAT file extension

Data File

Data Files

PART file extension

Partially Downloaded File

Misc Files

UUE file extension

Uuencoded File

Encoded Files

AIF file extension

Audio Interchange File Format

Audio Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

CER file extension

Internet Security Certificate

Web Files

TGA file extension

Targa Graphic

Raster Image Files

ASPX file extension

Active Server Page Extended File

Web Files

VCXPROJ file extension

Visual C++ Project

Developer Files

CPP file extension

C++ Source Code File

Developer Files

PNG file extension

Portable Network Graphic

Raster Image Files