A blocklist is a maintained list of domain names that are known to serve a particular kind of content. They are used by filtering software, schools, workplaces and security tools to decide what to block. A domain’s presence on a list is a statement made by the people who curate it, usually after the site has been seen hosting that kind of content.
Why it matters
Blocklists give a firm answer where other checks give a probable one. Reading a page and guessing its topic can be wrong. A domain that appears on a curated adult or gambling list has been identified by someone already. That is why a blocklist match is the strongest evidence in a Link Signals report, and why it is treated as confirmed.
How Link Signals uses them
Link Signals checks each destination’s hostname, and its parent domains, against the lists below. A match is a confirmed Not safe verdict. So a link to a.b.example.com is caught when example.com is listed. The check happens before the page is fetched, so a listed site is reported even if it no longer loads.
| List | Domains |
|---|---|
| Adult | 61,159 |
| Gambling | 2,690 |
| Violence | 23 |
The reason shown depends on context. If the page carrying the link is itself about that topic, the reason says the domain is on the blocklist. If it is not, the link is reported as out of context as well.
Common misunderstandings
- Not being on a list does not make a domain safe. Lists cover adult, gambling and violence. Pharmacy spam, loans and similar are found by reading the page instead, so they are weaker evidence.
- Lists age. A domain can change hands after it was listed, so the verdict describes the domain’s record, not necessarily what is on the page today.
- A match does not mean your site has been hacked. A link to a listed site may be one you added knowingly, for example on a news story.
Sources, coverage and limits are on blocklist sources.
Questions
Can a blocklist match be wrong?
Rarely, but a domain can be listed in error or have been cleaned up. Check the destination yourself, and see false positives if you think a match is mistaken.
What if my link is to a listed site on purpose?
Mark it as reviewed or ignore it. See ignore a finding.
Run a scan and find where these show up on your own site.
