Technical SEO

Find pages with a missing canonical tag

A canonical tag tells search engines which URL is the main version of a page. Lastmod crawls the pages in your sitemap and lists the ones that have none.

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What the problem is

The same page can be reachable on more than one URL: with and without tracking parameters, with a trailing slash or without. A canonical tag names the version you want to be found and counted.

Without one, search engines pick a version themselves. A canonical is a strong hint, not a command, so the tag does not guarantee the choice, but a page with no hint at all leaves the decision entirely to them.

example-bakery.comOpportunities

Illustrative data

Missing canonical

/blog/eu-vat-guide-2026

What's going on: This page has no canonical tag. Without one, search engines have to guess which URL is the main version.
What to do: Add a canonical tag that points to the preferred URL of this page.
Evidence: Found in the latest crawl
No canonical tag in the page's HTML
Page is listed in your sitemap

Lastmod never edits your site. You make this change yourself, then tell Lastmod what you changed.

How Lastmod finds it

The page has no canonical tag.

Needs

Access to your domain (verified, or through Search Console) and an XML sitemap

What you do

Open the task
It names the page, shows that no canonical tag was found in its HTML, and says what to add.
Add the canonical tag
Put a canonical link in the page's head that points to the preferred URL of that page, usually the page itself. Lastmod never edits your site; you or your developer make the change.
Mark the task done and enter the tag
Lastmod then fetches the page and looks for the tag, and starts measuring.

example-bakery.comTasks

Illustrative data

Missing canonicalMeasuring

How the result is measured

Measuring needs a working Search Console connection; without its data there is no baseline to compare against, so a task made without it gets its implementation checked, not its clicks. About 30 minutes after you mark the task done, Lastmod fetches the page and looks for your new text, and says so when it can't check. It then follows daily clicks for 28 days against the 28 days before, and waits 3 days for Search Console data to settle. The result says how reliable the measurement is; with fewer than 400 impressions in the baseline the answer is “not enough data”, never a percentage. A result is not proof that the change caused it.

How Lastmod finds this problem →Canonical tag →XML sitemap →All the kinds of opportunity Lastmod finds →

See if it applies to your site

Start the 30-day free trial. Technical checks run as soon as Lastmod has access to your domain and can read your sitemap.