A canonical tag is a line in a page's code that tells search engines which web address is the real version of that page, when the same content can be reached at more than one address. It goes wrong when it points at a different page, an address that redirects, another website, or a page that's hidden from search. Second Opinion flags those conflicts. A page with no canonical tag isn't a failure on its own.
Your homepage probably lives at more than one address. With the www and without it. With a slash at the end and without one. Sometimes with .html on the end, sometimes not.
To you, those are all the same page. To a search engine, they're separate addresses that happen to show the same thing.. and it has to pick one to list.
A canonical tag is how your site tells it which one.
What a canonical tag is
It's one line in the code of a page that says, in effect: "If you find this content at several addresses, this is the real one." Google treats it as a strong hint about which address gets the credit.
When it's right, you never think about it. When it's wrong, nothing looks broken to a visitor. The page loads fine. Google just quietly prefers a different address than the one you'd pick.
How it goes wrong
- It points at a different page. Often a copied template, where every page's tag still points at the homepage.
- It points at an address that redirects. The tag names an address that doesn't really exist anymore. It just forwards somewhere else.
- It points at another website. Usually left over from a theme demo, or a site that was copied from another one.
- It points at a page hidden from search. The tag calls a page the real one while that page is marked noindex.
The redirect version is the one that catches careful sites. Hosting platforms sometimes add or remove .html, or a trailing slash, after the tag was written. The tag still names the old form of the address, so now it points at something that forwards. You can't see it unless you check.
What we check
Second Opinion reads the canonical tag on your pages and flags the conflicts above. It doesn't flag a page just because the tag is missing. Most small sites are fine without one, because Google is usually good at picking the obvious address on its own.
This check is part of the crawlability half of your Website Score.
Check yours in fifteen minutes
You need your browser and one page at a time.
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Find the tag
Open the page, right-click, choose View page source, and search the page (Ctrl+F, or Cmd+F on a Mac) for the word canonical. You're looking for a line that contains rel="canonical" and a web address.
If there isn't one, that's usually fine. Move on to the next page.
For each of your main pages, you know whether it has a canonical tag and which address it names.
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Check that it names this page
The address in the tag should be the address of the page you're on. If you're on your drain cleaning page and the tag names your homepage, that's the most common version of this problem.
Every canonical tag you found names the page it sits on, not a different one.
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Paste the address and watch the bar
Copy the address from the tag and paste it into a new browser tab. Then look at the address bar once the page loads.
If the address changed, even by a slash or a .html, the tag is pointing at a redirect. Ask whoever maintains your site to update the tag to the final address.
Each canonical address loads exactly as written, with nothing changing in the address bar.
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Re-run the audit
Once any fixes are live, run a fresh Second Opinion audit. We read the tags live, so the check updates right away. Google's own choice of address catches up as it comes back through your pages.
Your new report shows no canonical conflicts on your key pages.