# Canonical Tag Checker: Make Sure Google Gets One Clear URL

> Free canonical tag checker: find rel=canonical in HTML and headers, confirm the target returns 200 and is indexable, and test www and https variants. No signup.

Enter a URL to see its declared canonical, whether that target is valid and indexable, and whether every version of your domain lands in one place.

- Use it free (no signup): https://yes-seo.com/canonical-checker
- API: `GET https://yes-seo.com/api/v1/canonical-checker?url=https://example.com`
- What it does: Canonical checker: finds rel=canonical in HTML and HTTP headers, checks it is absolute, self-referencing or intentional, returns 200 and is indexable, and tests http/https and www/non-www variants redirect to one version.

The same content often lives at several addresses: with and without www, over http and https, with tracking parameters or a trailing slash. A canonical URL tells search engines which version you want indexed and shown, so links and other signals are consolidated instead of split across duplicates.

This canonical checker finds the rel=canonical declared in a page’s HTML and HTTP headers, checks that it is absolute and either self-referencing or clearly intentional, and confirms the target returns 200 and is indexable. It also tests the http, https, www and non-www versions of your domain to make sure they redirect to a single one.

## How to check a canonical tag

1. **Enter the page URL** — Use the address you want to rank, or a variant with parameters to see where it points.
2. **Review the canonical** — See where it is declared, its target, and whether that target answers 200 and can be indexed.
3. **Check host variants** — Confirm http, https, www and non-www all redirect to the same version, then fix any that don’t.

## How Google chooses a canonical

A canonical tag is a strong hint, not a directive. Google weighs several signals and picks the version it considers best ([Google Search Central](https://developers.google.com/search/docs/crawling-indexing/consolidate-duplicate-urls)):

- **Redirects:** a strong signal that the target should be canonical.
- **rel=canonical** in the HTML or HTTP header: a strong signal.
- **Sitemap inclusion:** a weak signal.

Internal links, HTTPS and hreflang clusters feed in too. When your signals agree, Google usually follows your choice. When they conflict, for example the canonical names one URL while the sitemap and internal links use another, Google decides for itself. URL Inspection in Search Console shows both the user-declared and the Google-selected canonical.

## How to declare a canonical correctly

Put a single link element in the `<head>`, with an absolute URL:

```

```

For PDFs and other non-HTML files, send it as an HTTP header:

```
Link: ; rel="canonical"
```

A self-referencing canonical on every indexable page is a sensible default: it neutralizes tracking parameters, session IDs and stray variants that other sites link to. Google only accepts rel=canonical in the `<head>`, and it advises against setting or changing it with JavaScript, so the version in your server HTML is the one to rely on. Background reading: [canonical tag](https://yes-seo.com/glossary/canonical-tag) and [duplicate content](https://yes-seo.com/glossary/duplicate-content).

## Canonical mistakes we see most

- **A broken target.** A canonical pointing at a URL that redirects, returns [404](https://yes-seo.com/http-status-codes/404) or carries noindex sends contradictory signals.
- **Every page canonical to the home page.** Usually a theme or plugin bug, and it asks Google to ignore the rest of your site.
- **Paginated pages canonical to page 1.** Google advises giving each page in a series its own canonical; see [pagination](https://yes-seo.com/glossary/pagination).
- **Mixed formats.** The canonical uses `http://` or drops the trailing slash while internal links use the other form.
- **Translations canonical to one language.** Each language version should be canonical to itself and linked with hreflang; verify with the [hreflang checker](https://yes-seo.com/hreflang-checker).
- **Canonical plus noindex** on the same page: two conflicting messages. Pick one.

## One host for the whole site

Your domain answers on four base URLs. Three should redirect to the fourth with a single 301:

| Variant | Expected result |
| --- | --- |
| http://example.com/ | 301 → https://www.example.com/ |
| http://www.example.com/ | 301 → https://www.example.com/ |
| https://example.com/ | 301 → https://www.example.com/ |
| https://www.example.com/ | 200, canonical to itself |

Choosing www or non-www makes no difference to rankings; consistency does. The [redirect checker](https://yes-seo.com/redirect-checker) shows exactly how each variant hops.

## Tips for clean canonicals

- Use exactly the same URL format in canonicals, internal links, sitemaps and hreflang tags.
- Strip tracking and sorting parameters from canonical URLs, but keep parameters that change the content, such as ?page=2 on a paginated list.
- Fix canonical logic in the template rather than page by page, so new pages inherit it.
- When you syndicate articles, ask partners to noindex their copies; Google no longer recommends cross-domain canonicals for syndication.
- After a domain migration, check that canonicals point to the new domain and not the old one.

## Limits to keep in mind

We read the canonical in the server HTML and HTTP headers; canonicals added or changed by JavaScript aren’t evaluated. The checker shows what you declare, not what Google finally selects; for that, inspect the URL in Google Search Console. Spotting duplicate content across many pages is beyond a single-page check, so use the crawl in the [website SEO audit](https://yes-seo.com/website-seo-audit) to find duplicate titles and descriptions site-wide.


## Frequently asked questions

### What is a self-referencing canonical?

It is a canonical tag that points to the page’s own URL. It confirms the preferred version and protects against duplicates created by parameters or by other sites linking to odd variants of the address.

### Should every page have a canonical tag?

It isn’t required, but Google recommends declaring one, and a self-referencing canonical on every indexable page is a safe default. Pages that are deliberate duplicates, such as print versions, should point to the main version.

### Is a canonical tag the same as a 301 redirect?

No. A 301 sends people and crawlers to the new URL; a canonical leaves both pages reachable and only asks search engines to index one. Redirect when the duplicate doesn’t need to exist for visitors, use a canonical when it does.

### Why is Google ignoring my canonical?

Usually because other signals disagree: internal links, the sitemap or redirects point elsewhere, the pages aren’t truly duplicates, or the canonical target has problems. Align the signals and make sure the target returns 200 without noindex.

### Can a canonical point to another domain?

Yes, cross-domain canonicals are supported, for example when the same store runs on two domains. For articles republished by partner sites, though, Google now recommends that partners noindex their copies instead.

### Can I use a relative URL in a canonical?

Google accepts relative URLs but recommends absolute ones. A path like /page can resolve to the wrong protocol or host on staging servers, http versions or alternative domains.