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

BAT file extension

DOS Batch File

Executable Files

7Z file extension

7-Zip Compressed File

Compressed Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

FNT file extension

Windows Font File

Font Files

OTF file extension

OpenType Font

Font Files

LOG file extension

Log File

Text Files

CRX file extension

Chrome Extension

Plugin Files

MP4 file extension

MPEG-4 Video File

Video Files

JS file extension

JavaScript File

Web Files

PS file extension

PostScript File

Vector Image Files

DNG file extension

Digital Negative Image File

Camera Raw Files

WMV file extension

Windows Media Video File

Video Files

ZIP file extension

Zipped File

Compressed Files

MPA file extension

MPEG-2 Audio File

Audio Files