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

CSR file extension

Certificate Signing Request File

Web Files

DAT file extension

Data File

Data Files

DOC# file extension

Microsoft Word Document

Text Files

ICO file extension

Icon File

System Files

INDD file extension

Adobe InDesign Document

Layout Files

PAGES file extension

Pages Document

Text Files

PIF file extension

Program Information File

Executable Files

PL file extension

Perl Script

Developer Files

SH file extension

Bash Shell Script

Developer Files

SLN file extension

Visual Studio Solution File

Developer Files

TARGZ file extension

Compressed Tarball File

Compressed Files

TXT file extension

Plain Text File

Text Files

WPD file extension

WordPerfect Document

Text Files

XLR file extension

Works Spreadsheet

Spreadsheet Files