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

BAK file extension

Backup File

Backup Files

CAB file extension

Windows Cabinet File

System Files

CLASS file extension

Java Class File

Developer Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

DLL file extension

Dynamic Link Library

System Files

LOG file extension

Log File

Text Files

MP4 file extension

MPEG-4 Video File

Video Files

PPS file extension

PowerPoint Slide Show

Data Files

PY file extension

Python Script

Developer Files

SWF file extension

Shockwave Flash Movie

Video Files

TEX file extension

LaTeX Source Document

Text Files

TIF file extension

Tagged Image File

Raster Image Files

WAV file extension

WAVE Audio File

Audio Files

WMV file extension

Windows Media Video File

Video Files

ZIP file extension

Zipped File

Compressed Files