IITC is a browser add-on that modifies the Ingress intel map. It is faster than the standard site, and offers many more features. It is available for desktop browsers, such as Chrome and Firefox, and as a mobile application.
Unfortunately, at the moment the official branch is not developed, the pull-requests on github are not processed. In October 2018, the intel map URL was changed, and it took more than a week for developers to release a revised build. This was one of the reasons for creating own build from source code with bugfixes and improvements.