Baidu, Alibaba, and Tencent (BAT) have built their leading market positions in Chinese online media on the back of the mobile revolution and an absence of foreign rivals. The big three’s rivalry in online advertising reflects a broader struggle over key gatekeeper roles in the Chinese online economy, albeit one shaped by state intervention. While benefiting from protectionism at home, BAT are weak in most foreign markets and links to the Chinese state may hamper international expansion, particularly in the US