With regard to exactly who is the other side of the trade, remember that you are using the broker's credit lines with his participating banks to execute the trades (I am talking about ECN models only). Therefore the broker technically must be the other side of the trade, even though you are dealing directly on the participating bank's prices. The bank hasn't extended you credit directly, which is why for instance Hotspot states that they are counterparty to all trades. This is (or should be) the same for all ECNs. The same is true if you use a prime broker for HotspotFXI or EBSprime. The name you see is the name of your prime broker, even though you are dealing with dozens of other market participants directly.