URL: /rules/core/canonical

---
title: "Canonical URL"
description: "Validates canonical URL presence and format"
---

Validates canonical URL presence and format

| | |
|---|---|
| **Rule ID** | `core/canonical` |
| **Category** | [Core SEO](/rules/core) |
| **Scope** | Per-page |
| **Severity** | warning |
| **Weight** | 6/10 |

## Solution

Canonical URLs tell search engines which version of a page is the "master" copy, preventing duplicate content issues. Every page should specify a canonical URL, typically pointing to itself. Add a `<link rel="canonical" href="...">` tag in the head section. Use absolute URLs and ensure consistency (with or without trailing slash, www vs non-www). For paginated content, point to the main page or use rel="prev/next".

## Enable / Disable

### Disable this rule

```toml squirrel.toml
[rules]
disable = ["core/canonical"]
```

### Disable all Core SEO rules

```toml squirrel.toml
[rules]
disable = ["core/*"]
```

### Enable only this rule

```toml squirrel.toml
[rules]
enable = ["core/canonical"]
disable = ["*"]
```