Which mobile site type does Google recommend using?

Google strongly recommends responsive design because it uses a single URL and a single HTML code base for all devices, simplifying crawling and indexing. This approach eliminates the need for Googlebot to crawl multiple versions of a page, making it more efficient. Dynamic serving, while using a single URL, delivers different HTML based on the user agent, which can be more complex to implement and prone to misconfiguration if not handled carefully. A separate domain (e.g., m.example.com) requires Google to crawl and index two distinct sites, manage duplicate content signals, and rely on correct annotation (rel="alternate" and rel="canonical") to understand the relationship between the desktop and mobile versions, which is more resource-intensive and error-prone.