By investigating dealer banks and high-frequency traders (HFTs) in foreign exchange markets, this study sheds light on the distinct yet complementary roles of ``traditional’’ and ``new’’ market makers in over-the-counter markets. Using message-level data, our findings reveal that these two types coexist by carrying out complementary roles. HFTs excel in processing public information, while dealers are skilled in managing private information. Specifically, HFTs provide resilient liquidity during market-wide volatility spikes, whereas dealer liquidity is robust in informational events such as scheduled macroeconomic announcements or policy regime changes. HFTs contribute to the majority of the information share through frequent quote updates, which incorporate public information. In contrast, dealers contribute to price discovery through trades that impound private information.