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

CLASS file extension

Java Class File

Developer Files

CPL file extension

Windows Control Panel Item

System Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

DAT file extension

Data File

Data Files

DOC# file extension

Microsoft Word Document

Text Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LOG file extension

Log File

Text Files

PDB file extension

Program Database

Database Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

SDF file extension

Standard Data File

Data Files

SH file extension

Bash Shell Script

Developer Files

SITX file extension

StuffIt X Archive

Compressed Files

TARGZ file extension

Compressed Tarball File

Compressed Files

TEX file extension

LaTeX Source Document

Text Files

TIFF file extension

Tagged Image File Format

Raster Image Files