File with a .GADGET extension contains a ZIP archive of network files and serves purposes of a small application – a GADGET for a rear bar in Windows Vista or Windows 7. Files contained within the archive can be in form of HTML code, JS scripts or CSS style spreadsheets – they can be unpacked by changing the .GADGET file extension into .ZIP. Installation files are stored within the system directory: Program Files/Windows Sidebar.

Initially, different types of gadgets were available with the Windows Live Gallery Service, however, presently it is no longer shared. Examples of GADGET type program are search and system tools, small games or RSS message channels.