A canonical tag (<link rel="canonical">) is an HTML element in the <head> of a page that tells search engines which URL is the "master" version of that page. It solves the duplicate content problem that occurs when the same content is accessible under multiple URLs.
The Duplicate Content Problem
WordPress often serves the same content under different URLs:
https://example.com/page/https://example.com/page/?utm_source=twitterhttps://www.example.com/page/http://example.com/page/
Without a canonical tag, search engines might index multiple versions, diluting your page's ranking power.
How It Works
<link rel="canonical" href="https://example.com/page/" />This tells search engines: "Regardless of which URL variant you found this page at, https://example.com/page/ is the one that should appear in search results."
WordPress and Canonical Tags
WordPress automatically generates canonical tags since version 2.9. SEO plugins like Yoast SEO and Rank Math provide more control over canonical URLs, allowing you to set custom canonicals for each page.
What InspectWP Checks
InspectWP checks whether your WordPress pages have a canonical tag and reports the canonical URL. Missing canonical tags are flagged as an SEO issue.