Personalized search is a customization of search engine results created by a filter that takes into account potentially relevant information such as the user’s history, location and preferences.
Google introduced personalized search in 2004, promoting it as a way to “understand exactly what you mean and give you back exactly what you want.” Google uses a combination of information from user search history, bookmarks and personalized Google+ pages, among other services that are tied to user accounts. Sites you tend to visit more often appear higher on search engine results page (SERP).
Although it has less information to go on, Google also attempts to provide personalized search to users that do not have a Google account and do not have search history enabled.
Microsoft Bing is another personalized search provider. Like Google, Microsoft has many pages and services a user might already interact with. Those sites and services yield information for customization of both search and advertisement results.
Personalized search is more useful for some types of searches than others. It’s convenient, for example, for finding local services and finding information on topics that you’ve researched before. For other types of searches, however, such as researching a new topic, the customization tends to yield less valid and relevant responses than would be the case for an unfiltered search.
One of the concerns raised by critics of personalized search is that it limits the user’s view of the Web. That limitation is sometimes referred to as a filter bubble, which effectively restricts the user’s perspective and the information available to them.
To disable personalized search in Google, add pws=0 at the end of a search URL. Another option is to click the gear icon in the top right and go to search settings > personal results > do not use personal results. Google also provides a bookmarlet: Turn off Google personalization. In Bing, click on the gear in the top right and go to: search history > turn off search history.