.SISX File Extension

Symbian OS Installation File - Nokia/Sony Ericsson/ Motorola

Compressed File
SISX files are similar, but incompatible, with their predecessor, the SIS file; the SISX file is only able to be used by systems that are running Symbian OS 9.1 or later.

The SISX file contains an installer for a various piece of software for a Symbian phone as well as a signature that verifies that the software installer package has not been changed.

These files are also similar to UIQ3 extension which is commonly used on Sony and Motorola phones running the Symbian OS.