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

CER file extension

Internet Security Certificate

Web Files

CFG file extension

Configuration File

Settings Files

HTML file extension

Hypertext Markup Language File

Web Files

CSR file extension

Certificate Signing Request File

Web Files

YUV file extension

YUV Encoded Image File

Raster Image Files

CAB file extension

Windows Cabinet File

System Files

JAVA file extension

Java Source Code File

Developer Files

MAX file extension

3ds Max Scene File

3D Image Files

ACCDB file extension

Access 2007 Database File

Database Files

DB file extension

Database File

Database Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

AZW file extension

Amazon Kindle eBook File

eBook Files

TARGZ file extension

Compressed Tarball File

Compressed Files

CS file extension

Visual C# Source Code File

Developer Files

7Z file extension

7-Zip Compressed File

Compressed Files