A dead link is three different problems wearing one name.

A dead destination returns an error or a redirect to somewhere irrelevant. It is found by requesting the URL.

A dead fragment resolves to no id on a page that exists. It is found by comparing the fragment against the destination's ids, and it is invisible to a plain status-code crawl.

A placeholder href is not a link at all: a bare #, an empty string, a JavaScript call that does nothing, or an example domain left from a documentation sample. Found by reading the markup.

Given markup or markdown, the check can extract every link and classify the obviously dead ones without any network access.

Anything about the destination itself: whether an external URL still resolves, whether it redirects repeatedly, whether it now returns a paywall, whether a page you link to has been removed.

External link rot is the largest category by volume and the slowest to check, because it depends on somebody else's server and somebody else's patience. Rate-limit the crawl, cache results, and re-check on a schedule rather than on every build.

Internal pages are cheaper: crawl your own site, collect ids and status codes, and compare against the link graph.

Generated content invents plausible URLs. A documentation link with the right shape and the wrong path is a failure mode that reads correctly and resolves to nothing.

It also reuses placeholders from examples, and it rewrites headings during editing, which breaks fragments that other pages depend on.

The result is a page that looks complete with three dead links in the middle, and the reader who clicks one concludes the product is abandoned.

Group by cause rather than by URL. One template emitting a placeholder href produces forty findings and one fix; forty separate dead links are forty fixes.

For each finding record the destination, the link text, the page it is on and the failure shape: status, fragment or placeholder. That is enough for somebody to repair it without re-running the audit.

Assign a recurring cause to the template owner, not to the content author. Most link rot is a pipeline problem.

Check placeholders and fragments on every publish, since that is cheap and catches the generated defects immediately.

Crawl external links weekly or monthly depending on volume, and re-verify everything before a campaign launch, when the landing pages matter most.

Retire findings rather than accumulating them. A link audit with two hundred open items and no owner is a monthly ritual, not a control.