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

AIF file extension

Audio Interchange File Format

Audio Files

BIN file extension

Binary Disc Image

Disk Image Files

CUE file extension

Cue Sheet File

Disk Image Files

CUR file extension

Windows Cursor

System Files

IFF file extension

Interchange File Format

Audio Files

INI file extension

Windows Initialization File

Settings Files

KEY file extension

Keynote Presentation

Data Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LNK file extension

Windows File Shortcut

System Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

SITX file extension

StuffIt X Archive

Compressed Files

TIF file extension

Tagged Image File

Raster Image Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

3DS file extension

3D Studio Scene

3D Image Files