Site Magic is UniFi's automated site-to-site VPN, configured from the UniFi Site Manager rather than from inside a single console. You pick the sites, pick which networks each site advertises, choose a topology, and the gateways negotiate WireGuard tunnels among themselves.
The appeal is that it removes the part of site-to-site VPN that consumes the afternoon: matching proposals at both ends, remembering which side initiates, and hand-writing static routes twice. Add a VLAN to a site later and you publish it into the mesh from the same screen.
Both topologies have real use cases. Full mesh gives every site a direct path to every other site, which is what you want when branches talk to each other; hub-and-spoke forces traffic through a designated site, which is what you want when a filtering appliance, an inspection point, or a compliance boundary lives at headquarters.
Site Magic routes rather than bridges, and in a mesh it does not NAT between sites. Ubiquiti is explicit about the mesh limit: NAT is unsupported, so overlapping subnets cannot exist inside the group. Two sites both using 192.168.1.0/24 leave no valid routing table, and the tunnel comes up while traffic goes nowhere useful.
Hub-and-spoke is the exception, and it is worth knowing before you renumber a site. Enabling Auto-Scale and NAT Spoke VPNs applies a source NAT rule that translates each spoke into its own /24 before routing it to the hub, so overlapping spokes can coexist.
The trade is direction. Sessions can then only be initiated by the spoke, and a resource on the spoke stays unreachable until you add a destination NAT rule for it by hand. Where more than a few resources need exposing, Ubiquiti's own recommendation is to design the subnets so they do not overlap.
Plan your addressing before you build the mesh rather than after. Give every site a distinct block, use a per-site third octet as the low-effort convention, and keep the scheme documented somewhere other than in the head of the person who set it up.
WAN changes are handled for you, which is a large share of the value. Because the gateways coordinate through your UniFi account instead of through static peer addresses, a site whose ISP rotates its address re-establishes its tunnels without anyone editing a configuration file.
Bandwidth, however, is still bounded by the slowest link in the path. A mesh does not create capacity, so a site on a thin upload will bottleneck every flow that traverses it — size that circuit for the traffic you actually intend to push across it.
Be aware that Site Magic is a closed system. Every endpoint must be a supported UniFi gateway adopted into your account, so a third-party firewall, a cloud network, or a client-owned appliance still requires the manual configuration described next.