Favicons are the website logos that are displayed in your browser’s address bar, tab title, history, and bookmarks. For example, if you visit the CRAN website () in Google Chrome, and look at the browser tab, you will see a small R logo. On mobile devices, favicons are also used in place of an App icon for websites that are pinned to the home screen.

Recall that this file can be injected into the document area using the YAML metadata:

  html_document:
      in_header: header.html

If you want to ensure that each browser or platform on which your document is viewed uses a version of your icon with optimal resolution for its specific layout, you may use a service such as https://realfavicongenerator.net to generate a set of favicons and a slightly more complex version of the header HTML code. This service is currently used by the pkgdown package’s pkgdown::build_favicon() function () to make a set of favicons out of R package logos.