> ## Documentation index
> Fetch the complete documentation index at: https://rankfield.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# How Site Strength works

> Learn how Rankfield calculates Site Strength from web graph ranks, and how to compare and interpret scores.

## What the score measures

Site Strength combines two standard ranks of each domain in the web graph: PageRank and harmonic centrality. Both rise when many domains link to a domain, and when the domains linking to it are themselves well linked.

Rankfield turns the two rank positions into a logarithmic scale and maps them to 0–100 with a calibration checked against held-out data. The mapping only goes up: a better rank never gives a lower score.

## Read it correctly

- Compare scores within the same release. Every answer is scored with the release in [Get Dataset Status](/docs/data/get-dataset-status).
- Treat a difference of a few points as noise. The score summarises a graph model.
- The score is not a probability, a share of the web or a count of backlinks.
- It does not measure traffic, rankings, relevance or trust.
- It is not interchangeable with Moz Domain Authority, Ahrefs Domain Rating or any other vendor's score: they use other data and methods.

## Which domains have a score

Only domains in the current web graph release, about 118 million. Others answer `200` with `"inGraph": false` and a `siteStrength` of `0`: the domain isn't in our link graph yet, so treat it as no data, not a score. The field is absent for every other domain, and a malformed domain gets `400`. A domain can be missing because the crawl data the graph is built from has no page linking to it, not because it has no links. [Coverage and dates](/docs/data/coverage-and-dates) has the details.