Do prefetched requests contain a referer: header?

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Yes, prefetched requests include a HTTP Referer: header indicating the document from which the prefetching hint was extracted.

This may impact referrer tracking that is commonly used on many sites. For this reason, link prefetching may not be appropriate for all content. However, it is possible to instruct Mozilla to validate a prefetched document when the user follows a href to the prefetched document by specifying the Cache-control: must-revalidate HTTP response header. This header enables caching, but requires an If-Modified-Since or If-None-Match validation request before the serving the document out of the browser's cache.