Mobile proxies route traffic through IP addresses assigned by cellular carriers rather than home ISPs or data centers, making them a distinct third category.
Why they're hard to block
Carriers assign IPs from a shared pool to huge numbers of mobile devices (a technique called CGNAT), which means blocking a mobile IP risks blocking many unrelated real users on the same carrier — sites are understandably reluctant to do that, making mobile proxies unusually resilient to blocking.
The tradeoffs
This resilience comes at a cost: mobile proxies are typically the most expensive category, speeds can be inconsistent since they depend on real cellular network conditions, and free mobile proxies are essentially nonexistent since carrier data isn't something that gets casually shared.
When they're worth it
For tasks facing aggressive IP-based blocking where even residential proxies get flagged, mobile proxies are often the last resort that still works, but they're rarely the starting point for casual or budget-conscious use.