Canonical changed by JavaScript

Error severity, in the JavaScript tab

Why it matters

Canonical tags injected or altered by scripts are a known cause of conflicting signals; Google may ignore them or pick the response version.

How to fix it

Emit the canonical tag in the HTML response and never modify it on the client.

How Crawlune finds it

Crawlune flags Canonical changed by JavaScript automatically on every crawl and lists the affected URLs under the JavaScript tab, where you can filter, inspect each page and export the list to CSV. The free version crawls up to 550 URLs with every check enabled.