Info: Potentially bad value sitemap for attribute rel on element link

[edent]

Summary

When using <link rel=sitemap …> the checker raises a warning.

URL for document that reproduces the problem

https://shkspr.mobi/blog/

HTML/CSS/SVG snippet that reproduces the problem

<link rel=sitemap href=https://example.com/sitemap.xml type=application/xml>

Checker error messages

Info: Potentially bad value sitemap for attribute rel on element link Typo for timemap?

Spec links/citations

https://html.spec.whatwg.org/multipage/links.html#other-link-types

That says:

Extensions to the predefined set of link types may be registered on the microformats page for existing rel values. [MFREL]

There is a rel="sitemap" registered on that site - https://microformats.org/wiki/rel-sitemap

While I don't have hard statistics, it is used in some popular CMS software, and appears to be widely used in open source projects:

• https://jekyllcodex.org/without-plugin/sitemap/
• https://docs.astro.build/en/guides/integrations-guide/sitemap/
• https://package.elm-lang.org/packages/canceraiddev/elm-pages/latest/Head
• https://github.com/search?q=+rel%3D%22sitemap%22&type=code

Steps to reproduce

1. Check a page with the rel="sitemap" attribute.
2. See error.

Expected behavior

Checker should be aware of the popular rels registered on microformats.

Actual behavior

An error occurs.

Screenshots or screen recordings

No response

[j9t]

There is a rel="sitemap" registered on that site - https://microformats.org/wiki/rel-sitemap

That is marked as “proposed” though. Just pointing it out—aware of this process but not clear about how and when a value is considered official and “standard.”

[edent]

Indeed, but so are things like amphtml and apple-touch-icon. Those are all valid in:

validator/src/nu/validator/datatype/RelValue.java

Lines 38 to 52 in b51a3e0

	/**
	* IANA-registered link relation types.
	* Source: https://www.iana.org/assignments/link-relations/link-relations-1.csv
	* Last updated: 2025-12-26
	*/
	private static final Set<String> registeredValues = new HashSet<>(Arrays.asList(
	"about",
	"acl",
	"alternate",
	"amphtml",
	"api-catalog",
	"appendix",
	"apple-touch-icon",
	"apple-touch-startup-image",
	"archives",

I assume the validator only uses the rel values from https://www.iana.org/assignments/link-relations/link-relations.xhtml

So I'll raise an issue at https://github.com/protocol-registries/link-relations/