What Google supports
Canonicalization is how Google picks one representative URL from a set of duplicates. You can state a preference with redirects, a rel="canonical" link (in HTML or an HTTP header), and by listing URLs in a sitemap. Google ranks these as a strong signal for redirects and rel=canonical, and a weaker signal for sitemaps. Combining consistent methods helps. None of them is required.
Google's current recommendations include: use a self-referential canonical on the preferred page; use absolute URLs; do not point a canonical at a noindex or error URL; do not use a URL fragment; do not use robots.txt or the removal tool as a substitute; and when you link on your own site, link to the canonical URL. If you use JavaScript, put the canonical in the HTML source and do not let scripts change it.
If you use both an HTML link and an HTTP header, Google supports that but warns it is easier to send two different URLs by mistake. Pick one method if you can.
Traffivio findings
missing_canonical means the public HTML audit did not find a non-empty canonical link. Google does not require every page to have one, so this is a prompt to check URL variants (http/https, www, trailing slash, parameters), not an automatic order to insert a tag.
multiple_canonicals means more than one canonical link element was present. That is more urgent: conflicting annotations are a common failure, and Google has documented that multiple rel=canonical values on a page may be ignored. Keep one intended URL, and make the sitemap and redirects agree with it.
Check a live URL with the meta tag checker. If you want Traffivio to propose a canonical change, the agent can draft it with a backup for you to approve. Nothing is written to the site until you say yes.
Official sources
Checked on 10 November 2026:
- How to specify a canonical with rel=canonical and other methods — supported methods, self-referential links, and what not to do.
- What is URL canonicalization — a preference is a hint, and Google may choose a different URL.
- Five common mistakes with rel=canonical — more than one rel=canonical on a page is ignored.
Review a canonical with a backup
Save the site in a Traffivio workspace. If a change is needed, the agent proposes it and waits for your approval before anything is applied.
Open the workspace ↗Questions
Do I have to add a canonical on every page?
No. Google says none of the canonicalization methods are required, and that if you do not specify a preference, Google will try to choose the best version to show. A self-referential canonical on the preferred URL is still recommended when you do declare a preference.
What happens if a page has more than one canonical?
Google's guidance on common mistakes states that when more than one rel=canonical is specified, all of them will be ignored. Current documentation also warns against giving different canonical URLs through different methods, such as a sitemap and a link element that disagree.
What do Traffivio findings missing_canonical and multiple_canonicals mean?
missing_canonical means the fetched HTML had no non-empty canonical URL. That is a low-severity signal and is not, by itself, a reason to add a tag. multiple_canonicals means more than one canonical link was found; that is worth reviewing so one intended URL remains.