This page serves as a documentation of used Nuclear Throne Together versions. Do note that this page may become outdated at any time and there many versions not being documented.
You can only play Co-op with people running the same version of Nuclear Throne Together as you.
NTT 9944
NTT 9944 is a beta Nuclear Throne Together version and one of the most popular alongside NTT 9940. Generally, the mod performance, compatibility and potential are better compared to 9940 but online Co-op connections are worse.
You can download it here. The Nuclear Throne discord is full of installation tutorials such as this one to help you get it running.
NTT 9940
NTT 9940 is the current stable build of Nuclear Throne Together and is generally considered the best for online Co-op.
You can download it here, with the page containing an installation tutorial.