What is "rankbrain"

RankBrain is a machine learning artificial intelligence system, the use of which by Google was confirmed on 26 October 2015. It helps Google to process search results and provide more relevant search results for users. In a recent interview, Google commented that RankBrain is the third most important factor in the ranking algorithm along with links and content.

If RankBrain sees a word or phrase it isn’t familiar with, the machine can make a guess as to what words or phrases might have a similar meaning and filter the result accordingly, making it more effective at handling never-before-seen search queries.

There are over 200 different ranking factors which make up the ranking algorithm, of which their exact functions in the Google algorithm are not fully disclosed, so it is impossible to know with 100% certainty. The general consensus is that RankBrain interprets the user searches to find pages that may not have contained the exact words that were used in the user search query. When offline, RankBrain is given batches of past searches and learns by matching search results. Once RankBrain's results are verified by Google's team the system is updated and goes live again.