Canonical URLs

What do duplicate URLs look like in real data?

Like extra pages. The two numbers above are both counts of AI crawlers fetching attensira.com's homepage over the 30 days to 4 October 2026, read over the Attensira MCP, and they differ by about two to one. Neither is wrong. The bot board keeps https://attensira.com/ and https://www.attensira.com/ as separate rows, so / shows 8,562 requests for one host. The evidence query counts both hosts as one page and shows 17,323. The two methods also count slightly differently, so read the 8,761 gap as mostly, not exactly, the www address. Same page, same window, two answers, because one report counts addresses and the other counts pages.

Citations split the same way. Links in stored ChatGPT answers often carry ?utm_source=chatgpt.com, a parameter ChatGPT appends itself, so one page can be cited under its bare address, its www address and a tracked copy of each. Any report that counts URLs literally turns every variant into another page. Pick one count per report, and give crawlers one address to fetch.

What is a canonical URL?

It is the one address you want search engines to treat as the main version of content that can be reached at several. The canonical link relation was defined in RFC 6596 in April 2012 as the preferred address from a set of resources that return the same content.

Duplicates arise constantly and mostly by accident:

• www and non-www, http and https;
• trailing slashes and letter case;
• tracking and session parameters (?utm_source=..., ?ref=...);
• sort, filter and pagination parameters;
• the same article under several paths or locales;
• printer-friendly and AMP-style copies.

How do you tell search engines which URL is canonical?

Google documents three signals, in order of strength:

• A redirect (301 or 308)

  Strength

  strong

  Use it when

  the duplicate should not exist for visitors at all, e.g. non-www to www

• <link rel="canonical" href="...">

  Strength

  strong

  Use it when

  the duplicate must stay reachable, e.g. a filtered or tracked URL

• Listing only the canonical in your sitemap

  Strength

  weak

  Use it when

  always, as a supporting signal

All three are hints. If you specify nothing, Google picks the version it thinks best, and it may pick differently from you when your signals disagree. Make them agree: redirect what should not exist, self-canonicalise every real page with an absolute URL, and list only canonical URLs in your XML sitemap. Search Console's URL inspection shows both your declared canonical and the one Google chose. See Google Search Console.

Why do canonicals matter for AI search?

Three reasons, all visible in our own data.

Signals split. Every citation, link and mention that lands on a duplicate is credited to a different address. Reports, and possibly engines, see two weaker pages instead of one stronger one.

Reports disagree unless they normalise. A tool that counts URLs literally shows one homepage as two pages, and two of our own reports differ by about two to one on the same page for that reason. Attensira's page report lists one row per cited URL, so a page cited at two addresses shows up as two rows you can see side by side.

Engines cite what they fetched. If a crawler can reach your page at several addresses, different answers may cite different ones. A redirect means there is only one to fetch. See crawling and indexing.

What are the objections to fixing canonical URLs?

"rel=canonical guarantees the URL." It is a strong hint. Conflicting signals, such as a canonical pointing at a page that redirects, can override it.

"Tracking parameters are harmless." For analytics, maybe. For indexing and citation counts, each one is another URL. Canonicalise parameterised URLs to the clean one.

"A relative canonical is fine." Google advises absolute URLs. A relative path resolved against the wrong base points the page somewhere unintended.

"Block the duplicates in robots.txt instead." Then crawlers cannot see the canonical tag on them, and links pointing at them are stranded. Redirect or canonicalise; do not hide. See robots.txt.

How does Attensira help?

Attensira's Pages report lists every URL of yours that AI answers cited, one row per exact URL, so a split between addresses is visible. The crew can then fix the redirects, canonical tags and sitemap in your repository as a pull request or in your CMS as a draft, after your approval. GitHub shows how a fix arrives as a pull request you can review line by line.