Enter a page URL to see whether its head survives parsing: the tag that closes it early, the metadata that landed in the body where Google ignores it, and every duplicate or malformed head tag.
Read the story behind this tool: Why Head Integrity Audit exists.
Related: Canonical Winning Shape / Duplicate Title + Meta Description Audit / Meta Tags + Open Graph Card Preview
The page is fetched once. The raw HTML is walked the way a browser's parser walks it, so the tool can name the first tag or text inside the literal head that forces the parser into body mode, then compares that with where the parsed DOM actually put each metadata tag.