Definition
A canonical URL is the representative URL for duplicate or substantially similar pages. For example, a product page and a tracking-parameter version may show the same content. A rel="canonical" link can identify your preferred version, but Google treats it as a signal rather than a command.
Why it matters
Duplicate URLs can split signals and make reports harder to interpret. Google generally attributes Search Console performance to the canonical URL. A duplicate may therefore show little traffic in its own report even when people reach that version.
Keep internal links, redirects and your XML sitemap consistent with the URL you want indexed. A canonical tag does not redirect visitors. A noindex directive has a different purpose: excluding a page from search. Avoid mixing conflicting instructions to solve duplication.
Where to check the canonical
In Search Console, inspect a URL and compare the user-declared canonical with the Google-selected canonical. These describe your declared preference and Google's indexed choice. A mismatch is a reason to investigate the content, links and redirect behavior; it does not automatically mean Google made an error.
URL Inspection reflects Google's available index data. After changing a canonical, Google needs to crawl and process the change before that choice may update.
Ask mowteng to compare URLs
mowteng can retrieve Google's index status, last crawl and canonical for a URL. Start with one unexpected duplicate, then use an index coverage audit to investigate a larger URL list.
Inspect this product URL and its parameter version. Compare their declared and Google-selected canonicals, index status and last crawl dates, and explain any mismatch.