The device commonly used to translate a URL into an IP address is a Domain Name System (DNS) server. When a user enters a URL in their browser, the DNS server resolves the human-readable domain name into a numerical IP address that computers use to identify each other on the Internet. This process involves querying authoritative DNS servers that hold information about domain names and their corresponding IP addresses. Efficient DNS resolution is critical for fast and reliable web browsing, making DNS an essential component of the internet infrastructure.