Navboost and click-based ranking signals revealed
US antitrust trial testimony revealed Navboost, a long-running Google system that uses aggregated click and query data to re-rank results.
What changed
During the US Department of Justice antitrust trial in the autumn of 2023, testimony from Google's head of search ranking described Navboost, a system dating to around 2005 that memorises aggregated user click behaviour on query-document pairs and uses it to adjust rankings. Related systems including Glue and slice-based navigation signals were also described. This was revealed through litigation rather than announced by Google, and Google has never published documentation on it. The disclosure changed the industry's understanding of how directly user interaction data feeds ranking, after years of Google publicly downplaying clicks as a ranking factor. Only the month of the key testimony is documented here.
Timing
Rollout began 1 October 2023. No completion date was announced. Rankings typically remain unstable for the whole rollout window, so measurements taken inside it are not a reliable read on the outcome.