# Search Engines & Sharing ## Introduction A search engine reads a page's title and description, and a chat app or social network reads its Open Graph and card tags to draw a preview of a link. `` sets all of them from the page, next to the title. The server writes them into the first document, which is the one crawlers and link previews read, and the browser keeps them current on every visit. This page covers the fields of `` and the sitemap and `robots.txt`, which Marmeon writes from your routes. The [pages](pages.md#the-document-head) page covers the title and the template around it. ## The head's fields ```tsx title="modules/notes/views/Show.tsx" ``` | Field | Writes | | ------------- | --------------------------------------------------------------- | | `description` | `` | | `canonical` | `` | | `robots` | ``, from `index` and `follow` | | `openGraph` | `og:*` as `property`, `article:*` for an article | | `twitter` | `twitter:*` as `name` | | `jsonLd` | `