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

C file extension

C/C++ Source Code File

Developer Files

CS file extension

Visual C# Source Code File

Developer Files

CSR file extension

Certificate Signing Request File

Web Files

ISO file extension

Disc Image File

Disk Image Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

OTF file extension

OpenType Font

Font Files

PL file extension

Perl Script

Developer Files

PS file extension

PostScript File

Vector Image Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

SRT file extension

SubRip Subtitle File

Video Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

TMP file extension

Temporary File

Backup Files

XCODEPROJ file extension

Xcode Project

Developer Files