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

ACCDB file extension

Access 2007 Database File

Database Files

APP file extension

Mac OS X Application

Executable Files

BAT file extension

DOS Batch File

Executable Files

BIN file extension

Binary Disc Image

Disk Image Files

DTD file extension

Document Type Definition File

Developer Files

FON file extension

Generic Font File

Font Files

KEY file extension

Keynote Presentation

Data Files

MP4 file extension

MPEG-4 Video File

Video Files

PDF file extension

Portable Document Format File

Layout Files

TAR file extension

Consolidated Unix File Archive

Data Files

UUE file extension

Uuencoded File

Encoded Files

VCD file extension

Virtual CD

Disk Image Files

VOB file extension

DVD Video Object File

Video Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

XLR file extension

Works Spreadsheet

Spreadsheet Files