Personalized search refers to search experiences that are tailored specifically to an individual's interests by incorporating information about the individual beyond specific query provided. Pitkow et al. describe two general approaches to personalizing search results, one involving modifying the user’s query and the other re-ranking search results.

While many search engines take advantage of information about people in general, or about specific groups of people, personalized search depends on a user profile that is unique to the individual. Research systems that personalize search results model their users in different ways. Some rely on users explicitly specifying their interests or on demographic/cognitive characteristics. But user supplied information can be hard to collect and keep up to date. Others have built implicit user models based on content the user has read or their history of interaction with Web pages.

There are several publicly available systems for personalizing Web search results (e.g., Google Personalized Search

Google Personalized Search

Google Personalized Search is a feature of Google Search and provided by Google. When a user is logged into a Google Account, all of their searches on Google Search are recorded into Google Web History...

 and Bing's search result personalization). However, the technical details and evaluations of these commercial systems are proprietary.