One of the checks
Where does the seat actually send you?
The other five checks are about the contract. This one is about the advertisement. A seat on this wall is a link, and a link is the only part of the arrangement that can reach into somebody's browser — so it is checked separately, and it fails in more interesting ways than the rest.
What it is
The thing being measured
We fetch the destination and record what it answered, we follow redirects and record where it ended up, and we submit the final URL to a safety service. Three separate facts, kept separate on purpose, because they mean three different things.
The distinction that costs the most to get right is between a link that is broken and a link that declined to answer us. Half the legitimate web sits behind a bot filter that returns 403 to anything without a browser. That is not a dead link — it is a link we could not confirm, which is a flag and a sentence, not a refusal.
Without taking our word for it
Check it yourself
Follow it yourself and watch where it lands.
# what it answers, and every hop on the way
curl -sI -L -o /dev/null -w '%{http_code} %{url_effective}\n' 'https://EXAMPLE'
# every redirect in the chain
curl -sIL 'https://EXAMPLE' | grep -i '^location:'
404, 410 or 5xx
Gone or broken. A dead advertisement, and a refusal.
403 or another 4xx
It declined to answer us. Flagged and stated, not refused.
A url_effective on a different domain
It redirects before it lands. Flagged, with the final host named.
No answer at all
Could be their host, could be our egress. Stated as such, and never published as a finding about them.
The safety-service half of this check needs an API key and cannot be reproduced with curl alone. Google's Safe Browsing site status page will tell you what it holds on a URL without one.
Our door policy
What we do with the answer
A destination that is gone, or that a safety service has flagged, is a refusal. A destination that answers evasively, or redirects before it lands, is a flag. A destination we could not submit for a check asserts nothing at all.
Every threshold on this site is published before it is applied. All of them, on one page.
Read this part
What this measurement does not establish
A link that is clean at the moment of purchase can change afterwards; the destination is not ours and we do not control what it serves tomorrow.
When a link was never supplied, nothing is checked and nothing is claimed. This distinction was learnt the hard way: we once published a refusal against a token with eleven million dollars of daily volume, whose stated finding was that no link had been supplied — by us, about a contract nobody had submitted. An absence is not a discovery.
A clean link is not an endorsement of what is behind it. It means the destination resolved and was not flagged at the moment we looked. We do not review the content of anybody's site.
The Wall sells twenty-four advertising seats and screens every contract before selling one. It is a door policy, not a rating: we have no opinion on whether anyone should hold, buy or sell anything, and we are not qualified to have one.
Where this check gets used
Every refusal is published, with its measurement
A badge nobody can audit is a marketing claim. The ledger · what last night's round found, counted and unnamed.