The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear test explosions. By prohibiting explosive testing, the Treaty effectively prevents countries from developing new nuclear weapons or significantly advancing existing ones. It also makes it extremely difficult for countries that do not have nuclear weapons to develop them.

The CTBTO has established an International Monitoring System (IMS) to ensure that no nuclear test explosion goes undetected. The data collected by the IMS has also been used for disaster mitigation such as earthquake monitoring and tsunami warning, as well as research into fields as diverse as whale migration, climate change and the prediction of monsoon rains. 

Info: ctbto.info/m/links