“Alternate page with proper canonical tag” means the page has a canonical tag that points to another URL, and Google agrees with it. Google indexes the canonical URL and keeps this one out. That is exactly what a canonical tag is for, so in most cases there is nothing to fix.
Typical members of this list are parameter URLs (?sort=, ?utm_source=), product variants that point to the main product, AMP or print versions, and the second URL of a pair such as /page and /page/.
When it is a problem
It is worth a look only if pages that should rank on their own are listed here. Export the list and scan it for:
- Main pages. A category or product page that points its canonical to the homepage or to another category. This often comes from a theme or plugin that writes one canonical for every page.
- Paginated listings. Page 2, 3 and so on with a canonical to page 1. Google then ignores the items that appear only on later pages. Each page of a listing should point to itself.
- Language versions. A translated page with a canonical to the English page drops out of the index; hreflang does not override that. Each language version should have a canonical to itself.
- Pages that are not really duplicates. If the canonical points to a page with different content, Google may still accept it for a while and then start ignoring it.
How to check a page
- Inspect the URL with URL Inspection. User-declared canonical shows the URL your page points to; Google-selected canonical shows what Google uses. In this report they match.
- Open the page source and search for
rel="canonical". Check there is exactly one, with an absolute URL. - Ask: should someone searching for this page's topic land on the canonical URL instead? If yes, everything is fine. If no, change the canonical to point to the page itself.
How to fix a wrong canonical
- Change the template or SEO plugin setting that writes the canonical, not individual pages.
- Use self-referencing canonicals on every indexable page: the canonical is the page's own clean URL.
- Keep internal links and the sitemap consistent with the canonicals, so all signals point the same way.
- After the change, inspect a few URLs and request indexing; the pages will leave this report over the next weeks.
What SignalCrawler checks here
The audit reads the canonical of every crawled page and flags the risky patterns: many pages pointing their canonical at the homepage, paginated pages pointing to page 1, canonicals that point to redirects, errors or noindex pages, canonicals on a different host or protocol, and pages with several conflicting canonical tags.