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

SYS file extension

Windows System File

System Files

INDD file extension

Adobe InDesign Document

Layout Files

CBR file extension

Comic Book RAR Archive

Compressed Files

CSR file extension

Certificate Signing Request File

Web Files

BAK file extension

Backup File

Backup Files

CFG file extension

Configuration File

Settings Files

AI file extension

Adobe Illustrator File

Vector Image Files

WAV file extension

WAVE Audio File

Audio Files

AIF file extension

Audio Interchange File Format

Audio Files

TMP file extension

Temporary File

Backup Files

BAT file extension

DOS Batch File

Executable Files

7Z file extension

7-Zip Compressed File

Compressed Files

RPM file extension

Red Hat Package Manager File

Compressed Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

MDB file extension

Microsoft Access Database

Database Files