How Google assesses the ‘authority’ of web pages
Google has no single authority metric but rather uses a bucket of signals to determine authority on a page-by-page basis.
Google’s fight against problematic content has drawn renewed attention to a common question: how does Google know what’s authoritative? The simple answer is that it has no single “authority” metric. Rather, Google looks at a variety of undisclosed metrics which may even vary from query to query.
When Google first began, it did have a single authority figure. That was called PageRank, which was all about looking at links to pages. Google counted how many links a page received to help derive a PageRank score for that page.
These days, links and content are still among the most important ranking signals. However, artificial intelligence — Google’s RankBrain system — is another major factor. In addition, Google’s ranking system involves over 200 major signals. Even our Periodic Table of SEO Success Factors that tries to simplify the system involves nearly 40 major areas of consideration.
None of these signals or metrics today involve a single “authority” factor as in the old days of PageRank, Google told Search Engine Land recently.