Blog
Articles on domain authority and the public web graph, in the same register as the methodology: what the numbers mean, and what they do not.
What is harmonic centrality? The link-graph measure behind domain authority
What harmonic centrality is: how close a domain sits to the rest of the web, a worked example, how it differs from PageRank and why link farms fail.
How to check domain authority for free: one domain, ten, or a whole watchlist
How to check domain authority for free: look up one domain, rank up to ten in one table, compare side by side, track over time, or use the free API.
What is a good domain authority score? What the numbers really mean
What a good domain authority score is: what OAR ranges mean, from the median domain to the top 1,000, and how to judge a score against real competitors.
How to read a domain's authority trend: steps, slides and gaps
How to read an OAR trend: what steps, slow slides and gaps mean, why one point is about a 20% rank change, and when a move is just noise between releases.
How to vet an expired or second-hand domain before you buy it
A pre-purchase checklist for expired and second-hand domains: link-graph history, PageRank vs harmonic centrality, archives, email, blocklists, trademarks.
Why domain authority scores disagree: DR, DA, Authority Score and OAR
Ahrefs DR, Moz DA, Semrush Authority Score and OAR give one domain four different numbers. What each one measures, why they diverge, and how to read them.