For new subscribers a lot of people use the chat notification.
New subscriber:
← :twitchnotify!twitchnotify@twitchnotify.tmi.twitch.tv PRIVMSG #CHANNEL :USER just subscribed!
Re-subscriber:
← :twitchnotify!twitchnotify@twitchnotify.tmi.twitch.tv PRIVMSG #kCHANNEL :USER subscribed for X months in a row!