Multipath DNS (mDNS)
Multipath DNS, most commonly implemented as mDNS (Multicast DNS, RFC 6762), enables devices on a local network to discover and resolve hostnames without a centralized [[dns|DNS]] server by multicasting queries to all devices on the local subnet. The .local pseudo-TLD is reserved for mDNS and must not be delegated in the public DNS. mDNS is implemented in Apple's Bonjour, Linux's Avahi, and Windows 10+ and is the backbone of zero-configuration networking (Zeroconf) for services like AirDrop, Chromecast, and smart home devices.
Example
When you print to printer.local on a Mac, Bonjour uses mDNS to broadcast a query over the local network. The printer responds with its IP address, and the Mac connects — no DNS server required.