In NoMachine Network, the Access Id is a unique security code used to protect a target machine from unauthorized access, ensuring only authorized users can connect. It acts as an additional layer of security beyond standard system credentials, designed for scenarios where machines are accessible over the internet. It works alongside the NoMachine Network Machine Id (the unique identifier for the computer) and User Id (your NoMachine account). 

It is entered when prompted after initiating a connection using the Machine Id. When publishing the computer to NoMachine Network, the Access Id is enabled by default, and it can be disabled if the owner prefers not to use it. Where to find it: the Access Id is configured in the Machine  >  Change availability settings on the host computer.