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

APP file extension

Mac OS X Application

Executable Files

CUE file extension

Cue Sheet File

Disk Image Files

DB file extension

Database File

Database Files

DBF file extension

Database File

Database Files

EPUB file extension

Open eBook File

eBook Files

IFF file extension

Interchange File Format

Audio Files

LOG file extension

Log File

Text Files

LUA file extension

Lua Source File

Developer Files

NES file extension

Nintendo (NES) ROM File

Game Files

PAGES file extension

Pages Document

Text Files

PART file extension

Partially Downloaded File

Misc Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

PY file extension

Python Script

Developer Files

TOAST file extension

Toast Disc Image

Disk Image Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files