How do OffLine Address Generators, Generate an Address not already used?

[blokHed]

Bitcoin, and Ethereum offline address/ key generators.
As they obviously are not live connected to the BlockChain, how is it they can generate an address/ key, that will be unique, and not conflict with what is already on the BlockChain?
EDIT: Excuse double post, not allowing delete.

[BurtW]

Bitcoin, and Ethereum offline address/ key generators.
As they obviously are not live connected to the BlockChain, how is it they can generate an address/ key, that will be unique, and not conflict with what is already on the BlockChain?
EDIT: Excuse double post, not allowing delete.

All Bitcoin addresses (including those generated by connected wallets) are assigned at random.  The reason we do not have to worry about collisions is that with a properly operating secure random number generator the probability of the same address being generated twice is, for all practical purposes, zero.

There are about 2¹⁶⁰ possible Bitcoin addresses.  That is an incomprehensibly large number.