Pages link to each other. Crawlers discover pages by following links.
The check looks at the links on the fetched priority pages: a page that links to nothing on your own site, or that nothing links to, is an island — hard to reach by crawling and read as isolated.
Crawlers discover pages by following links. A page reachable only from the sitemap is found late and rarely re-read; a page that links nowhere ends the crawl. Internal links are also how engines learn which pages belong together.
From a priority page, count the links to other pages on your domain. From the homepage, can you click to every page that matters in two steps?
What the agent does: the agent lists the dead ends; the links are editorial and belong to you.
Part of the 23 checks · group: Page content — text without JavaScript, response time, internal links, answer-first structure, self-contained sections, headings/dates/authorship.
No — the check reads the links on the pages it fetched. It finds islands among the priority pages, not across the whole site.
The page check reads your public pages from outside and runs all 22 — free, no signup, no AI engine involved.