Personalization is also known as customization or microtargeting and consists of tailoring a product or service to accommodate the needs of specific individual customers, instead of broader target markets. It involves focused targeting efforts at the level of the individual, the household, or a small group of customers. Personalization grew in popularity since the 1980s, because of the availability of electronic scanner data. Commercial direct marketers and firms mined large and sophisticated databases to target specific consumer segments. Given the exponential growth of social media and “big data” analysis in the 21th century, marketers have further finessed their personalization strategies. This entry examines the history of personalization and its potential problems, including the increased risk of privacy breaches.