Check a Domain's Common Crawl Harmonic Centrality

Look up a domain in Common Crawl's published domain web graph. The result reports its Harmonic Centrality position and value, PageRank position, percentile, graph release and the exact coverage of our local lookup index.

Dataset lookup only. Scan.now does not contact the website. Results come from the named Common Crawl graph snapshot and state the local index coverage. How we scan · Acceptable use

How it works

Normalise the domain
A URL is reduced to its public hostname. No request is sent to the website because this is a dataset lookup, not a live crawl.
Query the published graph
Scan.now searches a local index built directly from Common Crawl's official domain rank file, ordered by Harmonic Centrality.
Read the result in context
Lower rank positions are better. The report shows the graph size, release vintage and indexed top-N coverage, and does not present the metric as a Google ranking factor.

What Common Crawl Harmonic Centrality measures

A domain-level view of how closely a website is connected to the rest of the observed public web.

Common Crawl builds a directed web graph from links found during its crawls. Each node represents a registered domain and each edge represents an observed link from one domain to another. Harmonic Centrality describes how quickly a domain can be reached from elsewhere through short link paths in that graph.

For a domain v, the measure adds the reciprocal of the relevant shortest path distance for every reachable domain u. A short path contributes more than a long path, while an unreachable domain contributes zero.

H(v) =∑1d(v,u) for every reachable domain u ≠ v

Lower rank position is better.Rank 1 is the most central domain in that graph release. The raw Harmonic Centrality value works in the opposite direction: a larger value means greater graph proximity.

Put this result in context

This scanner answers one part of the review. Continue with SEO Audit for crawl, titles, links, speed, structured data, then Tech Stack Scanner for cms, frameworks, analytics, cdn and hosting. These are separate checks because a strong result here does not prove that the adjacent surface is healthy.

For the background behind these signals, read Website Security: What a Vulnerability Scan Looks For and How to Fix It and How to Read a Security Scan Report: Severity, False Positives and What to Fix First. The Scan.now methodology explains request limits, scan boundaries and what the scanner deliberately does not attempt.

How to read your Common Crawl rank report

The checker preserves the published measurements and adds context rather than inventing a proprietary authority score.

HC position

Your position when domains are sorted by Harmonic Centrality. A position of 8,000 ranks ahead of 20,000.

HC value

The underlying sum of reciprocal graph distances. It is useful for comparing releases without relying only on ordinal position.

Graph percentile

The percentage of domains in the complete release ranked at or below this domain. It makes a large rank easier to interpret.

PageRank position

A separate link-based ordering that weights incoming links by the importance of the domains supplying them.

Harmonic Centrality compared with PageRank

Both use the same web graph, but they answer different questions.

Measurement	Main question	What tends to improve it	Important limitation
Harmonic Centrality	How close is this domain to the rest of the reachable graph?	Connections that create short paths through well-connected parts of the web.	Proximity does not prove quality, trust, relevance or traffic.
PageRank	How much importance flows to this domain through incoming links?	Editorial links from domains that themselves receive meaningful links.	It does not understand the topic, intent or quality of a page.

Current lookup data

A published snapshot, with its coverage shown

Scan.now currently uses Common Crawl release cc-main-2026-jul-aug-sep. The local lookup contains the first 1,000,000 domains ordered by Harmonic Centrality from a graph of 133,241,980 domains.

Open the official rank file

A snapshot, not a live index

Links can be added or removed after a graph is published. Always compare the release name before comparing two results.

Unranked does not mean absent

An unmatched domain can fall below our indexed top-N cutoff, use another registered domain, or be missing from that crawl sample.

Domain-level aggregation

Subdomains are combined under their registered domain. The result describes the domain graph, not the strength of one page or hostname.

How this fits into an SEO review

Use centrality as external link-graph context alongside crawlability, content and technical evidence.

Harmonic Centrality is not a Google ranking factor and Scan.now does not convert it into a claim about search position. It can still answer a useful diagnostic question: is the domain deeply connected to the web graph observed by Common Crawl, or does it sit outside the indexed leading portion?

A technically strong website can have low graph visibility because few external sites link to it. A central domain can still have broken canonicals, blocked pages, duplicate titles or weak content. That is why this checker remains separate from the SEO audit.

Guides for this tool

Background reading written to go with these results.

13 min read · Updated Sep 13, 2026 Website Security: What a Vulnerability Scan Looks For and How to Fix It

A website vulnerability scan checks the parts of a site an attacker can reach without logging in: Transport security, HTTP headers,...

Read the guide

9 min read · Updated Sep 18, 2026 How to Read a Security Scan Report: Severity, False Positives and What to Fix First

A scan report is a list of findings with severities, and the hard part is deciding what matters. How severities are assigned, how to...

Read the guide

Frequently asked questions

What is Harmonic Centrality?

It sums the reciprocal of the shortest link-path distance from a domain to other reachable domains in the graph. A highly central domain is close to many other domains through short paths.

Is this a Google ranking factor?

No. This is a measurement from Common Crawl's open web graph, not a Google metric. It can help compare web connectivity, but it does not predict a search position on its own.

Why can a domain be unranked here?

The local lookup index contains the top-N rows of the named Common Crawl release. An unmatched domain can sit below that cutoff, use another hostname, or be absent from that snapshot. The result states the cutoff rather than calling the domain nonexistent.

Is this live backlink data?

No. Common Crawl publishes periodic graph snapshots built from completed crawls. Every result names its release so you can judge its age.

What is the difference between Harmonic Centrality and PageRank?

Harmonic Centrality measures proximity across the graph. PageRank distributes importance through incoming links. They answer related but different questions, so the report shows both without combining them into a proprietary score.