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

ACCDB file extension

Access 2007 Database File

Database Files

CSR file extension

Certificate Signing Request File

Web Files

CUR file extension

Windows Cursor

System Files

PL file extension

Perl Script

Developer Files

DOC# file extension

Microsoft Word Document

Text Files

TXT file extension

Plain Text File

Text Files

MPG file extension

MPEG Video File

Video Files

7Z file extension

7-Zip Compressed File

Compressed Files

JSP file extension

Java Server Page

Web Files

CLASS file extension

Java Class File

Developer Files

TAR file extension

Consolidated Unix File Archive

Data Files

PPS file extension

PowerPoint Slide Show

Data Files

3DM file extension

Rhino 3D Model

3D Image Files

3GP file extension

3GPP Multimedia File

Video Files

PNG file extension

Portable Network Graphic

Raster Image Files