Search engine optimization different signals. The leading search engines, Google, Bing, and Yahoo, do not disclose the algorithms they use to rank pages. Some SEO practitioners have studied different approaches to search engine optimization, and have shared their personal opinions. Patents related to search engines can provide information to better understand search engines. In 2005, Google began personalizing search results for each user. Depending on their history of previous searches, Google crafted results for logged in users. In 2007, Google announced a campaign against paid links that transfer PageRank. On June 15, 2009, Google disclosed that they had taken measures to mitigate the
Search engine privacy DuckDuckGo. There have been several well publicized breaches of search engine user privacy that occurred with companies like AOL and Yahoo. For individuals interested in preserving their privacy from search engines, there are many routes available to them, such as using an anonymity software like Tor that attempts to separate the user's location and information from their search. Search engines generally have privacy policies in order to inform users about what data of theirs they may be collecting and what purposes it may be used for. While these policies may be an attempt at transparency by search engines, many people