The biggest multiplayer platform. Over 3000 active players online playing, hundreds of games hosted every 5 mins, spectate/late spectate any live game without limitations, messenger client, free technical support, help forums, rating system, games saved on your profile and more. Voobly employs Userpatch.
Another good multiplayer platform for Age of empire 2 HD edition. It has over 1000 active players online playing, Steam workshop, limited spectator mode, access to three additional extensions: African kingdoms & Forgotten Empires, Rise of Rajas; discussion forums, rating system and more. Steam is also base on Userpatch.
Another famous multiplayer platform for Age of Empires 2. It has around 400 - 800 players online playing and the messenger client. However, Gameranger has one of the best "p2p multiplayer latency" which allows playing without any lag. 1.0/1.0c patches are the most commonly played.
Mostly an Asian platform. It has over around 1000 players but all of them are from Vietnam, China, and few other Asian countries. If you are from a different continent, use VPNGATE: www.vpngate.net and set the location to Vietnam or any Asian country so you can view the age of empires 2 lobbies.