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

BIN file extension

Binary Disc Image

Disk Image Files

CAB file extension

Windows Cabinet File

System Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

MOV file extension

Apple QuickTime Movie

Video Files

MOBI file extension

Mobipocket eBook

eBook Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

CSR file extension

Certificate Signing Request File

Web Files

MDB file extension

Microsoft Access Database

Database Files

JAVA file extension

Java Source Code File

Developer Files

PCT file extension

Picture File

Layout Files

7Z file extension

7-Zip Compressed File

Compressed Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

UUE file extension

Uuencoded File

Encoded Files

GBR file extension

Gerber File

Data Files

LOG file extension

Log File

Text Files