Should every page have a canonical tag?

Yes, self-referencing, on every indexable page. It is the cheapest defence against duplicate URLs created by tracking parameters, sorting and case differences.

Can I use canonical instead of a redirect?

Only when both URLs must remain reachable. If one version should not be served at all, a 301 redirect is stronger and unambiguous.

Does a canonical guarantee which URL is indexed?

No. It is a strong hint that search engines weigh alongside internal linking, sitemaps and redirects. Contradictory signals cause them to pick their own.

Can a canonical point to another domain?

Yes, and that is the correct pattern for syndicated content. The receiving domain must cooperate, and the target must return 200 with equivalent content.

Network & DNS🌐 YAS server-sideAPI availableadvanced

Canonical Checker

Fetches a page and checks its canonical link tag and robots meta directives.

Processed by YAS · not stored

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What does this tool do?

Fetches a page and checks its canonical link tag and robots meta directives.

Why would I use it?

Duplicate content is hurting SEO and you suspect canonicals.
You want to verify the canonical points where it should.
You are auditing a site's indexation signals.

Real-life example

Input

https://example.com/page

Output

canonical: https://example.com/page
robots meta: index, follow

Both the <link rel=canonical> and robots meta are shown.

Input → Process → Output → Next

Input: Enter a URL.
Process: YAS fetches the page and extracts the canonical and robots tags.
Output: The canonical URL and meta directives.
Next action: Fix mismatched canonicals and noindex directives.

Common mistakes

Checking pages that block fetchers (auth/JS-rendered).
Assuming canonical = the page you are on (it may differ).
Ignoring the robots meta which can contradict the canonical.

What the result means

The canonical tells search engines which URL is the preferred version.

Privacy & security

Your input is sent to YAS infrastructure because the tool requires server-side processing or public network queries. Input is not stored.

API

Endpoint

POST https://yas.sh/api/v1/tools/canonical-checker

Request Header

Content-Type: application/json

cURL

curl -X POST "https://yas.sh/api/v1/tools/canonical-checker" \
  -H "Content-Type: application/json" \
  -d '{"url":"https://example.com/page"}'

JavaScript

const res = await fetch("https://yas.sh/api/v1/tools/canonical-checker", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
  "url": "https://example.com/page"
}),
});
const data = await res.json();

Python

import requests

r = requests.post("https://yas.sh/api/v1/tools/canonical-checker", json={"url":"https://example.com/page"})
data = r.json()

Field	Type	Required	Description
url	string	Yes	http/https URL

Success response

{ "title": "...", "canonical": "...", "noindex": false, "nofollow": false }

Check a page's canonical link, robots meta, and title.

Error responses

400 VALIDATION_ERROR — invalid input or unsupported option.
413 PAYLOAD_TOO_LARGE — input exceeds the 64 KB limit.
429 RATE_LIMIT_EXCEEDED — rate limit exceeded (60 req/min).

Limits

Maximum input: 64 KB per request.
Rate limit: 60 requests/min per IP address.
Authenticated accounts benefit from higher tier quotas.

How Canonical Checker works

A canonical link element or Link HTTP header names the preferred URL for a piece of content. When several URLs serve substantially the same content — with tracking parameters, alternate sort orders, or both www and apex variants — the canonical tells search engines which one to consolidate ranking signals onto. It is a strong hint, not a directive: search engines can and do select a different canonical when other signals disagree.

The check verifies the mechanics that decide whether the hint is honoured: the canonical must be an absolute URL, appear in the document head (or as a header), be self-referencing on the preferred version, and point at a page that returns 200 rather than a redirect or an error. A canonical pointing at a noindexed or redirecting URL produces contradictory instructions, and search engines resolve that contradiction unpredictably.

When to use it: real-world scenarios

Fixing duplicate content from URL parameters

Filter, sort and session parameters multiply URLs. Self-referencing canonicals on the clean URL consolidate signals rather than splitting them.

Auditing a migration

After a domain or path change, canonicals frequently still point at the old URLs, which quietly tells search engines to prefer the pages you just retired.

Resolving a www versus apex split

Both hostnames serving identical content without a consistent canonical divides link equity between two versions of every page.

Checking syndicated content

When a partner republishes your article, a cross-domain canonical on their copy attributes the original to you.

Pro tips

Use absolute URLs including the scheme. Relative canonicals are permitted but are resolved against the base URL, which is one more thing to get wrong.
Every indexable page should carry a self-referencing canonical. It costs nothing and eliminates an entire class of parameter-induced duplication.
Never combine a canonical with a noindex on the same page. You are simultaneously saying 'this is the preferred version' and 'do not index it'.
Canonical and hreflang must agree: each hreflang variant should self-canonicalise, not point at the other language.

Limitations and edge cases

What this tool deliberately does not do, and where it will disagree with other implementations.

A canonical is a hint. Search engines may choose a different URL if internal links, sitemaps or redirects contradict it.
Only the declared canonical is inspected; the checker cannot know which URL a search engine has actually selected.
Canonicals injected by client-side JavaScript may not be seen by all crawlers and are not evaluated here.
Cross-domain canonicals depend on the other site's cooperation and can be ignored.

Frequently asked questions

Should every page have a canonical tag?: Yes, self-referencing, on every indexable page. It is the cheapest defence against duplicate URLs created by tracking parameters, sorting and case differences.
Can I use canonical instead of a redirect?: Only when both URLs must remain reachable. If one version should not be served at all, a 301 redirect is stronger and unambiguous.
Does a canonical guarantee which URL is indexed?: No. It is a strong hint that search engines weigh alongside internal linking, sitemaps and redirects. Contradictory signals cause them to pick their own.
Can a canonical point to another domain?: Yes, and that is the correct pattern for syndicated content. The receiving domain must cooperate, and the target must return 200 with equivalent content.

Related tools

robots.txt Viewer Open Graph Preview