app/views/application/_favicon.html.erb
<link rel="apple-touch-icon" sizes="180x180" href="<%= asset_path 'favicon/apple-touch-icon.png' %>">
<link rel="icon" type="image/png" sizes="32x32" href="<%= asset_path 'favicon/favicon-32x32.png' %>">
<link rel="icon" type="image/png" sizes="16x16" href="<%= asset_path 'favicon/favicon-16x16.png' %>">
<link rel="manifest" href="<%= asset_path 'favicon/site.webmanifest' %>">
<link rel="mask-icon" href="<%= asset_path 'favicon/safari-pinned-tab.svg' %>" color="#5bbad5">
<link rel="shortcut icon" href="<%= asset_path 'favicon/favicon.ico' %>">
<meta name="msapplication-TileColor" content="#ffffff">
<meta name="msapplication-config" content="<%= asset_path 'favicon/browserconfig.xml' %>">
<meta name="theme-color" content="#ffffff">