How OAR is computed

The data source

Common Crawl publishes a web-scale hyperlink graph roughly monthly; each release is built from about three months of crawling. The release’s domain-level ranks file lists over 120 million registrable domains with two independent signals: a harmonic-centrality rank and a PageRank rank within that release’s graph. The files are openly downloadable from commoncrawl.org, so any score here can be checked against the raw data.

The formula (OAR v1)

Each rank maps to a logarithmic position between 0 and 1, so rank 1 scores highest and the long tail decays smoothly. The two signals combine with harmonic centrality as the primary weight:

f(rank) = 1 - ln(rank) / ln(N)
OAR = round(100 x (0.7 x f(hc_rank) + 0.3 x f(pr_rank)))

N is the total number of domains in the release’s graph. The result is clamped to 0 to 100.

What the scale means in practice

Authority on the web is roughly power-law distributed: a small set of domains attracts most links and everything else forms a very long tail. A linear scale would score all but the top few million domains as an indistinguishable 0, so OAR is logarithmic. For a recent release of about 121 million domains, with both ranks equal:

The median domain scores in the low single digits. That is deliberate: on this scale a 40 is already a strong position in the graph, and the numbers should say so rather than flatter.

Why two signals, weighted 0.7 / 0.3

Harmonic centrality measures how close a domain is to the rest of the web — the sum of reciprocal shortest-path distances from all other domains. Inflating it requires links from many places that are themselves close to the whole web, which makes it expensive to manipulate. PageRank, by contrast, is famously inflatable with link farms: dense clusters of low-value domains linking at a target measurably raise its PageRank while barely moving its harmonic centrality. Weighting harmonic centrality at 0.7 keeps the primary signal manipulation-resistant; PageRank at 0.3 preserves useful information about raw link volume.

Versioning

Every stored score records the algorithm version that produced it. Version 1 — the formula on this page — is frozen: any change to the formula, the weights, or the missing-data policy ships as a new version alongside the old one and is recorded in the changelog. Historic scores keep the version that produced them, so old and new numbers are never silently mixed.

Refreshes

When Common Crawl publishes a new release, every known domain is re-scored against it and a new point is added to its history. Scores are per release, so a trend chart shows how a domain moved across crawls, not day-to-day noise.

Honesty rules

• A domain that is provably absent from a release’s graph gets a gap in its history, never an estimated number.
• If we cannot prove absence (for example while a release is still being indexed), the page says so instead of guessing.
• Scores are never adjusted manually, bought, or boosted.

Limitations

• OAR is relative to each release’s graph. A score can move because the web around a domain moved, not because the domain changed.
• It is domain-level. Pages, subfolders, and individual URLs are not scored.
• It measures position in the public link graph — not content quality, trustworthiness, or traffic.
• It predicts nothing about search rankings. OAR is not an SEO metric, and nothing on this site promises ranking or traffic outcomes.
• New and very small domains often have too little presence in the graph for an honest number; they usually appear once other sites link to them.
• Freshness follows the data: scores update when a new release is ingested, not in real time.

Independence and trademarks

domainrating.org and its operator are not affiliated with, endorsed by, or connected to Ahrefs, Moz, or Common Crawl. “Domain Rating” and “Domain Authority” are trademarks of their respective owners; they are named on this site only to state that OAR is not those metrics.

OAR is not Ahrefs Domain Rating and not Moz Domain Authority. Those metrics are built on proprietary crawlers and private link indexes, and their numbers are not comparable to OAR or to each other. OAR is an independent scale; compare OAR to OAR.

Questions this page doesn’t answer are probably on the FAQ.