Technical SEO FAQ · JavaScript SEO & Rendering
How can JavaScript affect canonical tags?
JavaScript can create or modify canonical tags.
Google can process a JavaScript-injected canonical, but Google's documentation recommends putting the canonical in the original HTML where possible and says not to use JavaScript to change the canonical to a different URL than the one specified in the original HTML.
Bad pattern:
<link rel="canonical" href="https://www.theseocentral.com/product-a">
then JavaScript changes it to:
/product-b
This introduces conflicting signals.
If JavaScript is required, the implementation should produce one consistent canonical.
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