---
title: "Canonical tag check — Lemwatch Help"
description: "Crawls your top pages and flags missing, self-referential loops, cross-domain, or conflicting canonical tags — the top-3 SEO indexation bug."
canonical: "https://lemwatch.com/help/canonical-tag-check"
source: "https://lemwatch.com"
---

# Canonical tag check

> Crawls your top pages and flags missing, self-referential loops, cross-domain, or conflicting canonical tags — the top-3 SEO indexation bug.

## Quick answer

 On every SEO crawl we extract <link rel="canonical"> and Link: rel=canonical headers, then check for missing, mismatched, or cross-domain values.

## What it checks

- Every crawled page has a canonical

- Canonical resolves to a 200 (not 3xx / 4xx)

- No cross-domain canonicals unless intentional

- HTTP header and HTML tag agree

## Where to find it in Lemwatch

 **Site details → SEO → Canonicals.**

## How to fix

- Add a self-referential canonical on every indexable page.

- On paginated pages, point canonical to page 1 only if content is duplicated.

- Kill conflicting canonicals in HTTP headers if you also set the HTML tag.

- Re-crawl.

## FAQ

### Do canonicals block indexing?

 No — they consolidate signals. Use noindex to block.

### Do CMSes get this right?

 WordPress + Yoast: yes. Shopify: often needs manual overrides on collection pages.

## Related

- Robots.txt check

- Hreflang tag check

- Structured data check


## Related

- [Help centre](https://lemwatch.com/help)
- [Robots.txt check](https://lemwatch.com/help/robots-txt-check)
- [Hreflang tag check](https://lemwatch.com/help/hreflang-tag-check)
- [Structured data (JSON-LD) check](https://lemwatch.com/help/structured-data-check)
- [Lemwatch pricing](https://lemwatch.com/pricing)
- [How does Lemwatch validate canonical URLs?](https://lemwatch.com/help/canonical-url-checks)
- [How do I cancel my subscription?](https://lemwatch.com/help/cancel-subscription)