On the surface, linked records seem a lot like a couple other kinds of DNS records supported by NS1 — namely, CNAME records (part of the standard DNS repertoire) and ALIAS records (an NS1-specific record type to solve limitations of CNAME records at the zone apex). But linked records are subtly different: CNAME records can result in additional DNS round trips, and ALIAS records need to do recursive lookups behind the scenes which can impact performance. Linked records solve both these issues for cases where the record you’re linking to is hosted by NS1, maximizing both performance and convenience.
Many organizations have multiple DNS zones where one zone is a “vanity domain” for a “real” zone. As an example, let’s say your main zone is mycompany.com, and you also have mycompany.io as a secondary zone. You want any records created in mycompany.com to also be available under mycompany.io — that is, www.mycompany.com and www.mycompany.io should point to the same place. Furthermore, as changes get made to the main mycompany.com zone, you want the changes to also be reflected in mycompany.io zone.You could create the two zones and keep them manually in sync, but that can be a real pain. Linked Zones allow you to create these vanity domains which point to the “real” (target) zones containing the records.