hi, i’m amr. when two urls show the same page, most teams add a rel=canonical tag and consider it settled. google’s documentation describes it as a signal, and ranks it next to two other methods.
what google says, in its own words
- rel=”canonical” is “a strong signal that the specified URL should become canonical”
- a redirect is also “a strong signal that the target of the redirect should become canonical”
- including a url in a sitemap is “a weak signal”
- the page lists the methods “in order of how strongly they can influence canonicalization,” and says they “can stack and thus become more effective when combined”
- “Don’t use the robots.txt file for canonicalization purposes,” because google may still index disallowed urls without their content
- it doesn’t recommend noindex for picking a canonical within one site, because “it will completely block the page from Search”
- none of the methods is required: “your site will likely do just fine without specifying a canonical preference,” and without one google picks the version it judges best to show
my reading, not google’s wording: a sitemap that lists a url you don’t prefer works against your own canonical tag, since the page says every page in a sitemap is suggested as a canonical.
what to check this week
- list the duplicate-url cases your site produces: tracking parameters, http and https, www and non-www, trailing slashes
- for each one, check whether it redirects to the preferred version or carries a rel=canonical pointing there
- open your sitemap and confirm it lists only the versions you prefer. i covered what google reads from a sitemap in an earlier post
- if a robots.txt rule is your only handling of duplicates, rethink it, using the robots.txt post as a starting point
where this stops applying
the page doesn’t say how often google picks a different canonical than the one you declare, and it gives no figures, so this post makes no claim about odds. i haven’t audited any site. the list above is a starting point.
start scaling — if your site produces several urls for the same page, a short duplicate-url review usually finds the loose ends. let’s connect.
Sources: Google Search Central, “How to specify a canonical URL with rel=canonical and other methods” (developers.google.com/search/docs/advanced/guidelines/duplicate-content). Figures are published product documentation, not verified results from Amr’s own client accounts.