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

CUR file extension

Windows Cursor

System Files

DLL file extension

Dynamic Link Library

System Files

DOC# file extension

Microsoft Word Document

Text Files

HTML file extension

Hypertext Markup Language File

Web Files

M4V file extension

iTunes Video File

Video Files

MDB file extension

Microsoft Access Database

Database Files

MSG file extension

Outlook Mail Message

Text Files

PDF file extension

Portable Document Format File

Layout Files

PPS file extension

PowerPoint Slide Show

Data Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

SH file extension

Bash Shell Script

Developer Files

TTF file extension

TrueType Font

Font Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

3GP file extension

3GPP Multimedia File

Video Files