Increasingly, retailers have access to better pricing technology, especially in online markets. Through pricing algorithms, firms can automate their response to rivals’ prices. What are the implications for price competition? We develop a model in which firms choose algorithms, rather than prices. Even with simple (i.e., linear) algorithms, competitive equilibria can have higher prices than in the standard simultaneous Bertrand pricing game. Using hourly prices of over-the-counter drugs from five major online retailers, we document evidence that these retailers possess different pricing technologies. In addition, we find pricing patterns consistent with competition in pricing algorithms. A simple calibration of the model suggests that pricing algorithms lead to meaningful increases in markups, especially for firms with superior pricing technology.