.XPI File Extension
File TypeMozilla Installer Package
This file is saved in a binary format, which requires a specific program to read its contents.
What is an XPI file?
An XPI file is a compressed installation archive used by various Mozilla applications, including Firefox, Thunderbird, and SeaMonkey. It may contain the primary components installed with the software, or may contain an software extension, such as a web browser plug-in.
XPI files can often be installed by simply dragging and dropping the file onto an open web browser window. The Mozilla software uses a component called XPInstall, (which includes Mozilla installer script) to install the XPI packages.