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

AZW file extension

Amazon Kindle eBook File

eBook Files

CER file extension

Internet Security Certificate

Web Files

CSV file extension

Comma Separated Values File

Data Files

EXE file extension

Windows Executable File

Executable Files

GZ file extension

Gnu Zipped Archive

Compressed Files

MPA file extension

MPEG-2 Audio File

Audio Files

OTF file extension

OpenType Font

Font Files

PIF file extension

Program Information File

Executable Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

THM file extension

Thumbnail Image File

Raster Image Files

TTF file extension

TrueType Font

Font Files

TXT file extension

Plain Text File

Text Files

VCXPROJ file extension

Visual C++ Project

Developer Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

7Z file extension

7-Zip Compressed File

Compressed Files