Alternate page with proper canonical tag
This GSC status means you have two or more URLs serving similar or identical content, and on this particular URL you declared a rel="canonical" pointing at a different page. Google respected the directive and indexed the canonical instead. It is the "well behaved duplicate" bucket - usually healthy, but always worth auditing to make sure the canonical target is actually the URL you want ranking.
What this GSC status means
Googlebot crawled this URL, found a <link rel="canonical" href="..."> tag pointing to a different URL, and selected that target as the canonical version. Signals like PageRank and content freshness are consolidated onto the canonical. This URL is classified as an "alternate" and is excluded from the index - it will not appear in search results, but the declared canonical will. This is exactly how canonicalization is supposed to work for duplicate content.
Common causes
- Tracking URLs with query strings (utm_source, gclid, fbclid) canonicalizing to the clean URL.
- Product variants (color, size, SKU) canonicalizing to the master product URL.
- Paginated pages (?page=2, ?page=3) canonicalizing to page 1.
- Printer-friendly or AMP versions canonicalizing to the main page.
- Mobile-specific URLs (m.example.com/page) canonicalizing to the responsive desktop URL.
- Category or tag archive pages pointing to a main hub page.
How it affects indexing
By itself, no negative impact - this is the intended outcome of using canonicals. The alternate URL is excluded but your canonical target gets all the ranking signals consolidated. Problems arise only if (a) the wrong URL is set as canonical, (b) the canonical target is excluded for another reason (noindex, 404, or redirect), or (c) alternate URLs sit inside your sitemap and waste crawl budget.
How to diagnose
Open GSC Page indexing and click "Alternate page with proper canonical tag". For any URL, run URL Inspection - the "User-declared canonical" and "Google-selected canonical" fields will both show the target. Confirm they match and that the target URL is actually indexed and ranking. If a valuable URL is being canonicalized away unintentionally, that is the real issue.
How to fix
1. For healthy cases (tracking URLs, paginated pages, variants): do nothing - it is working. 2. Remove alternate URLs from your sitemap.xml - only submit canonicals. 3. If a URL should be standalone (unique content, not a duplicate), remove its rel="canonical" tag pointing elsewhere, or change it to self-referential. 4. If the canonical target is wrong, update the <link rel="canonical" href="CORRECT_URL"> tag in the alternate page's head. 5. Make sure the canonical target returns 200 OK, has no noindex, and is not itself being redirected. 6. Keep canonical URLs absolute (https://example.com/page), not relative, to avoid resolution ambiguity. 7. Use URL Inspection > Request Indexing on the canonical to refresh Google's view.