Confirm a page points search engines to the right canonical URL.
Canonical Tag Checker fetches a page and reads its <link rel="canonical"> tag, telling you exactly which URL that page is declaring as its authoritative version — and whether that declaration points back to itself or somewhere else entirely, which changes how search engines index it.
Many sites unintentionally serve the same content under multiple URLs — with and without a trailing slash, with and without tracking parameters, over both HTTP and HTTPS, or under both a www and non-www hostname. Search engines treat each unique URL as a potentially separate page unless told otherwise, which can dilute ranking signals across duplicates instead of consolidating them onto one strong version. A canonical tag is the page's own explicit instruction: "index this URL as the true version of this content, even if you found me somewhere else."
A self-referencing canonical — where the tag points back to the exact URL you requested — is the normal, healthy state for most standalone pages. A canonical pointing to a different URL is intentional and correct in specific cases, such as a print-friendly or parameter-tracked version of a page correctly pointing back to its clean primary URL; but it can also be an unintentional bug, such as an entire section of a site accidentally canonicalizing to the homepage, which would tell search engines not to index those pages' unique content at all.
This checker also surfaces the page's meta name="robots" tag alongside the canonical result, since the two interact: a page can have a perfectly correct canonical tag but still be excluded from search entirely by a noindex directive, which is a separate and equally important signal to check when auditing a page's search visibility.
Not necessarily fatal, but not ideal — without one, search engines infer the canonical version using their own heuristics, which is less predictable than declaring it explicitly, especially for sites with any URL duplication.
This is standard for syndicated content — a site republishing another site's article will often canonicalize back to the original source to avoid being seen as duplicating someone else's content.
In most cases yes, for search indexing purposes — but it doesn't prevent users from directly visiting or sharing the duplicate URLs; for a hard redirect, a 301 is the stronger fix.
It tells search engines not to index this specific page in results, but to still follow and credit the links found on it — commonly used on thin or utility pages that shouldn't rank themselves.
It's considered a best practice to self-reference on every indexable page, even when there's no known duplication risk yet, since it removes ambiguity for search engines by default.
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