What this tool checks
The checker fetches your page the way a crawler does (following redirects, recording the final URL) and extracts the tags that matter for search: the <title> element, meta description, rel="canonical", meta robots, every og:* and twitter:* tag, the H1 count and the lang attribute on <html>. Each one is scored against the same thresholds our full site audit uses, so a pass here is a pass there.
Why these tags matter
The title tag is still the strongest on-page ranking signal and the headline of your search result — if it is missing, duplicated, or truncated mid-sentence, you lose both relevance and clicks. The meta description does not move rankings, but it is the sales copy under that headline; when it is absent or the wrong length, Google substitutes whatever page text it finds, which is rarely persuasive. The canonical tag protects you from your own URL variants: session parameters, UTM tags and trailing-slash duplicates all split link equity unless a canonical consolidates them. And one stray noindex in a robots meta tag — often left over from a staging deploy — silently removes the page from Google entirely, which is why the tool treats it as a hard failure.
How to fix the common failures
Title too short or too long:rewrite to 30-60 characters with the primary keyword near the front and the brand at the end ("Primary Keyword — Qualifier | Brand"). Description out of range:aim for 70-160 characters that answer "why click this result?" — include the keyword once, since Google bolds matching terms. Missing canonical: add <link rel="canonical" href="https://…"> pointing at the clean, https, parameter-free URL — most CMSs and frameworks (Yoast, Next.js metadata, Shopify themes) can emit it automatically. Missing OG image: add a 1200×630 image via og:image; it is the single biggest visual upgrade to how links to your site look in feeds and chats. Unexpected noindex:check your CMS's "discourage search engines" setting and any SEO plugin defaults, then recrawl.
Meta tags are page-level, so checking one URL only tells you about that URL. Templates break in bulk — an e-commerce category template with a broken title pattern breaks every category at once. A full crawl catches those repeats across the whole site.