The Hilltop algorithm is a search ranking algorithm designed to identify the most authoritative documents and web pages on a given query topic. It operates on a special index of “expert documents,” which are non-affiliated lists of pages related to a specific topic. Links and anchor texts on the expert documents are then used to determine the authority of the target pages.
Unlike the PageRank algorithm, which only measured the “link authority” of a page, the Hilltop algorithm took into account the “topical authority” of the page.
The algorithm was developed by Krishna Bharat and George A. Mihăilă and was acquired by Google in 2003 for use in Google News results.
The Hilltop algorithm is important because it laid the foundation for modern ranking algorithms and thus defined modern SEO practices.
Hilltop may have introduced concepts such as link relevance, topical authority, expertise, and affiliation between websites.