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

BAK file extension

Backup File

Backup Files

CUR file extension

Windows Cursor

System Files

DMP file extension

Windows Memory Dump

System Files

INDD file extension

Adobe InDesign Document

Layout Files

PDF file extension

Portable Document Format File

Layout Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RPM file extension

Red Hat Package Manager File

Compressed Files

SRT file extension

SubRip Subtitle File

Video Files

SYS file extension

Windows System File

System Files

TXT file extension

Plain Text File

Text Files

WMV file extension

Windows Media Video File

Video Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

3DS file extension

3D Studio Scene

3D Image Files

3G2 file extension

3GPP2 Multimedia File

Video Files