Should you really add a canonical tag on ALL your pages, even the main ones?

Why does Google emphasize canonical tags even for unique pages? 

The search engine encounters daily URL variations that point to the same content: tracking parameters, session IDs, versions with or without a trailing slash, HTTP/HTTPS protocols. Without explicit instruction, the algorithm must guess which version to canonicalize.

A self-referencing canonical tag (the page points to itself) acts as a clear signal: "Here is THE official version." Even if your site does not deliberately generate duplicates, technical variations can appear in crawl logs — creating authority dilution.

What is the difference between a page with and without a canonical tag? 

Without a canonical tag, Googlebot applies its own heuristics to choose which version to index. This often works, but not always as you wish. As a result: the indexed version could be the one with a UTM parameter, the one in HTTP instead of HTTPS, or the one with a trailing slash when your internal structure does not use it.

With an explicit canonical, you maintain control. You tell Google: "No matter how you got here, index this precise URL." It's a safeguard, not a miracle solution — but a useful safeguard.

In what cases does the absence of a canonical tag really pose a problem? 

E-commerce sites with filters and sorting are the first concerned. The same logic applies to platforms that add tracking parameters, CMS that generate URLs with and without a slash, or multilingual sites with complex redirection management.

On a simple blog with clean URLs and strict architecture, the impact is marginal. But as soon as there is a layer of technical complexity — pagination, AMP versions, syndicated content — the canonical tag becomes an essential safety net.

• A self-referencing canonical clarifies which URL to index, even in the absence of deliberate duplicates.
• It protects against uncontrolled technical variations (parameters, protocols, trailing slash).
• Its absence leaves Googlebot to arbitrate alone, with a risk of undesired canonicalization.
• The impact is maximal on sites with filtering, tracking, or complex URL architecture.
• On simple sites, it is a good defensive practice rather than an urgency.

Is this recommendation consistent with ground observations? 

Yes, overall. Crawl audits regularly show cases where Google indexes the wrong version of a URL in the absence of a canonical tag. A typical example: a product page with ?sort=price canonicalized instead of the clean version, simply because the bot crawled it first or it received more internal links.

However, Google remains vague about the actual degree of risk. Saying "to avoid any ambiguity" is a cautious phrasing but does not quantify the frequency of the problem. On well-structured sites, the absence of a self-referencing canonical does not systematically trigger a disaster. [To be checked]: Google does not publish any metrics on the percentage of poorly canonicalized pages due to the lack of an explicit tag.

What nuances should be added to this rule? 

The first nuance: a canonical does not compensate for a flawed URL architecture. If your CMS generates 15 URL variants for the same page, the real problem is structural. The canonical limits the damage; it does not solve the cause.

The second point: the canonical is just a signal, not an absolute directive. Google can ignore it if other signals (301 redirects, internal links, sitemaps) point to a different URL. In case of conflict, the engine arbitrates — and it does not always go in your favor.

In what cases can this practice create complications? 

On highly dynamic sites with on-the-fly generated content, a poorly configured canonical can block the indexing of legitimate variations. For example: a news site with "city + event" pages where each combination is unique, but the CMS mistakenly applies a generic canonical.

Another case: sites with separate mobile versions (m.example.com) where a self-referencing canonical on mobile would conflict with the alternate desktop tag. Here, the canonical should point to the desktop version, not to itself.

What should you do concretely on your site? 

Step one: audit strategic pages. Check the source code of your main pages (homepage, categories, product sheets, flagship articles) to see if a <link rel="canonical"> tag is present. If it's missing, add it pointing to the preferred URL — usually, the page itself.

Second action: configure your templates. Most CMS (WordPress, Shopify, PrestaShop) allow enabling the self-referencing canonical through a plugin or a native option. On WordPress, Yoast and Rank Math do this by default. On custom systems, integrate the tag in the <head> of your PHP/Twig/etc. templates.

How can you check that your implementation is correct? 

Use Screaming Frog or Sitebulb to crawl your site and extract all the canonical tags. Filter the pages without a canonical, then cross-reference with your strategic pages. A good indicator: 100% of your indexable pages should have a canonical, even if 90% point to themselves.

Also check in Google Search Console, under the "Coverage" section: URLs marked "Detected, currently not indexed" or "Crawled, currently not indexed" may reveal canonicalization conflicts. If Google is not canonicalizing as you wish, the absence of an explicit tag is often to blame.

What mistakes should you absolutely avoid? 

Never create circular canonicals: page A points to B, page B points to A. Google ignores the signal and makes its own choice. Also, ensure that your canonical tags use absolute URLs (https://example.com/page) rather than relative ones (/page), even if Google tolerates relative URLs — it's best to remove any ambiguity.

Avoid mixing canonical and noindex tags on the same page: it's contradictory. If a page should not be indexed, it does not need a canonical. Finally, do not canonicalize to a 301 page, 404 page, or a page blocked by robots.txt — it's an inconsistent signal that undermines Googlebot's trust.

• Add a self-referencing canonical on all indexable pages (homepage, categories, product sheets, articles).
• Configure CMS templates to automatically generate the tag in absolute URL.
• Crawl the site with Screaming Frog to identify pages without a canonical.
• Check in Search Console for any canonicalization conflicts (detected pages not indexed).
• Eliminate circular canonicals, canonicals pointing to 404/301, and noindex pages with canonical.
• Test on a few pages before mass deployment to avoid template errors.