<Head .../>
Mounts its children into document.head. When a new child is inserted there the runtime detects tags that should be unique and replaces the existing one in place, so multiple pages/components can all contribute to the head without duplicates.
# Deduplication
Every element inserted into document.head (via <Head/>, a portal, or the renderer directly) is checked against the existing head. If a match is found by the rules below, the existing element is replaced with the new one.
| tag | matched by |
|---|---|
| <title> | there can only be one — any existing title |
| <meta> | same name attribute, or same property attribute |
| <link rel="canonical"> | any existing canonical link |
Tags that aren't in this list are appended as usual; they are not deduplicated.