Every link on the page is requested and its status recorded. A 404 or 410 means the destination states the resource does not exist. Only those two statuses count as broken - a 403 or 429 means our checker was refused, which is reported separately and never scored.
Impact is importance multiplied by the confidence tier’s weight — SPECIFICATION 1.0, RESEARCH 0.7, EMERGING 0.3, EXPERIMENTAL 0.1. Two rules backed by the same class of evidence therefore always carry the same weight, which is what makes the score reproducible rather than hand-tuned.
Built at scan time by link resolver, not from our static registry. That engine evaluates its whole rule set in one pass, so this check cannot be run on its own — it runs as part of a scan.