Software installer file for devices that use Symbian OS 9.1 or later; includes cell phones that support the Nokia S60 3rd Edition platform and devices that use the UIQ 3 platform; S60 is used in Nokia and Samsung smartphones, while UIQ 3 is mainly used in Sony Ericsson and Motorola phones.

SISX files are similar to .SIS files, but are only compatible with devices running Symbian 9.1 and later. Both SIS and SISX files are created using the MakeSIS tool and are signed by the SignSIS utility. The "makesis" and "signsis" commands are both invoked by the CreateSIS application.