RankBrain

What is RankBrain?

RankBrain is a machine learning (ML) component of Google's ranking algorithm, first confirmed by Google in October 2015. It was designed to help Google better understand ambiguous, unusual, or never-before-seen search queries by mapping them to related queries or concepts Google already understands. Google stated it was the third most important ranking signal at the time of its announcement.

What Problem Does RankBrain Solve?

Before RankBrain, approximately 15% of daily searches were queries Google had never seen before. Traditional keyword matching algorithms struggled with these novel queries. RankBrain uses word vectors (mathematical representations of words and phrases) to map unfamiliar queries to semantically similar, known queries — and returns relevant results even without exact keyword matches.

How RankBrain Works

• Takes an unfamiliar query and converts it into a mathematical vector (a set of numbers)
• Finds the queries and content that are closest to that vector in mathematical space
• Returns results that matched similar known queries, even without exact keyword overlap

RankBrain and SEO

RankBrain evaluates pages primarily based on user satisfaction signals:

• CTR — if users click your result for a query, RankBrain interprets it as relevant
• Dwell time — long visits suggest the content satisfied the user
• Pogo-sticking — returning to the SERP quickly signals dissatisfaction

What This Means for SEO

Because RankBrain focuses on satisfying search intent:

• Optimise for topics and concepts, not just exact-match keywords
• Use natural language that matches how people talk about a topic
• Make content genuinely better at satisfying user intent than competitors'
• Improve CTR through compelling title tags and meta descriptions