Canonical tag
A canonical tag tells search engines which URL should be treated as the main version of similar or duplicate pages. Check it when: Google indexes the wrong URL or pages compete with each other.
Last reviewed April 2026 by TheFreeSEOToolKit editorial workflow.
SEO audit terms, explained without the fog machine
Use this glossary when an audit warning sounds technical but you need to know what it means, whether it matters, and what to check next.
Noindex
A noindex directive asks search engines not to include a page in search results. Check it when: a page should rank but does not appear in Google.
H1 heading
The H1 is usually the main visible heading on the page. It should make the page topic clear quickly. Check it when: the page feels vague, generic, or mismatched with the title tag.
Schema markup
Schema is structured data that helps search engines understand page entities, breadcrumbs, FAQs, articles, products, or local business details. Check it when: a page could be eligible for richer search presentation.
Response compression
Compression such as gzip or Brotli reduces transferred page weight. Check it when: pages feel heavier than they should or performance tools flag uncompressed text assets.
Crawlability
Crawlability means search engines can discover and fetch the page. Check it when: robots.txt, redirects, server errors, or broken internal links may block access.
Internal links
Internal links connect pages on the same site. They help users, crawlers, and search engines understand which pages matter. Check it when: important pages are buried or isolated.
Meta description
The meta description is a short summary search engines may use in snippets. It is not a direct ranking lever, but it can affect click appeal. Check it when: search results look unclear or unconvincing.
Thin content
Thin content is a page that does not provide enough original value for its purpose. Check it when: a page ranks poorly, looks repetitive, or has been flagged in an AdSense review.