# Canonical

Set canonical URLs in Thulite SEO to prevent duplicate-content issues, using either a custom frontmatter value or the page permalink default.

The `rel` HTML attribute defines the relationship between a linked resource and the current document. A `canonical` value defines the preferred URL for the current document, which helps search engines reduce duplicate content.

## Settings

You can set a custom `canonical` URL in the frontmatter of a page:

```md
---
seo:
  canonical: "" # custom canonical URL (optional)
---
```

If you do not specify a custom canonical URL, the [Permalink](https://gohugo.io/methods/page/permalink/) of the current page is used (default).

## Generated meta tag

Thulite SEO generates the following meta tag — for example:

```html
<link rel="canonical" href="https://seo.thulite.io/docs/basics/canonical/">
```