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

7Z file extension

7-Zip Compressed File

Compressed Files

CUR file extension

Windows Cursor

System Files

BAK file extension

Backup File

Backup Files

VCXPROJ file extension

Visual C++ Project

Developer Files

DEB file extension

Debian Software Package

Compressed Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

KMZ file extension

Google Earth Placemark File

GIS Files

PY file extension

Python Script

Developer Files

ASP file extension

Active Server Page

Web Files

TEX file extension

LaTeX Source Document

Text Files

EPUB file extension

Open eBook File

eBook Files

DLL file extension

Dynamic Link Library

System Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

CLASS file extension

Java Class File

Developer Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files