If you are planning to add Recently Viewed products to your website then always use default magento approach. below approach is deprecated.
Because its not fully compatible with FPC so,now days magento using knockoutJS for Recently Viewed products.
If you need to add a 'Recently Viewed' products block specifically via layout xml, use the same class Magento\Catalog\Block\Widget\RecentlyViewed which the 'Recently Viewed' Product widget uses.
This will render a simple grid with the last 4 products view by the user.
You can configure...