'''{{vanchor|DNS-SD}}''' (DNS Service Discovery<ref name="dotorg">{{Citation | ref = dotorg | url = http://www.dns-sd.org/ | title = DNS-SD}}</ref>) allows clients to discover a named list of service instances and to resolve those services to hostnames using standard DNS queries. The specification is compatible with existing unicast DNS server and client software, but works equally well with mDNS in a zero-configuration environment. Each service instance is described using a DNS SRV<ref>{{IETF RFC|2782}}</ref> and DNS TXT<ref name="IETF RFC|1035">{{IETF RFC|1035}}</ref> record. A client discovers the list of available instances for a given service type by querying the DNS PTR<ref name="IETF RFC|1035"/> record of that service type's name; the server returns zero or more names of the form <Service>.<Domain>, each corresponding to a SRV/TXT record pair. The [[SRV record]] resolves to the ___domain name providing the instance, while the TXT can contain service-specific configuration parameters. A client can then resolve the A/AAAA record for the ___domain name and connect to the service.
Service types are given on a first-come-first-serve basis. A service type registry was originally maintained by DNS-SD.org,<ref name="dotorg" /> but has since been merged into IANA's registry for DNS SRV records.<ref>{{Citation | url = http://www.dns-sd.org/ServiceTypes.html | publisher = DNS-SD | title = Service types}}</ref>
