Google introduced RankBrain in 2015 as a machine-learning system used to help process search results.
Google confirmed RankBrain publicly on October 26, 2015, although it had already been operating for several months. The system helped Google interpret search queries, especially unfamiliar or conversational searches, by identifying relationships between words and concepts rather than relying only on exact keyword matches.
RankBrain was described as a machine-learning-based component of Google Search and was reported to be one of the most influential ranking factors at the time. It did not replace PageRank or the rest of Google’s ranking systems; instead, it worked alongside many signals involving links, content, relevance, freshness, and user context.
A frequent misunderstanding is that RankBrain is a single complete search algorithm or a chatbot. It is better understood as a machine-learning component within Google’s broader ranking and retrieval systems. BERT, introduced later, also used machine learning but focused more directly on understanding language context in queries.