Should og:image and og:url put in <meta> or <link>?

Question

For og:image and og:url, since they have URL, can I place them in a link tag instead of a meta tag, and is it preferable?

Answer 1

You must use link instead of meta if the value is a URL.

From the definition of the meta element:

The meta element represents various kinds of metadata that cannot be expressed using the […] link […] elements.

But a URL can of course be expressed using a link element (as it’s its purpose).

If you use a meta element for a URL value, RDFa parsers would extract a string value instead of a URL value. This also means that they wouldn’t be able to apply relative references against the base URL.

Example

Let’s say these elements are in a document with the URL http://example.com/foo:

The value from the link element is the URL http://example.com/bar.
The value from the meta element is the string /bar.

However, in the case of OGP …

The examples in OGP’s documentation use the meta element for URL values; there is no example with a link element.

While this means that many of their examples are invalid HTML+RDFa, and RDFa parsers will extract strings instead of URLs in those cases,
it may be the case that Facebook (or any other consumer) isn’t actually using RDFa to parse the content, and it may be the case that they don’t support link elements.

Note: These are just possibilities, judging from the quality of their documentation. I don’t have any experience/insight, as I don’t use Facebook. So you might want to test it with Facebook if you care about their OGP-based features.