The full documentation covers everything in detail. These are the questions that come up most.
Because it is true, and it is the design. Android probes VPN networks, and NetCage’s tunnel genuinely has nothing at the far end — that absence is what blocks the traffic. The notice is cosmetic and nothing is broken.
No. Android allows one VPN at a time, so connecting another one stops NetCage. NetCage reports that plainly rather than competing for the slot.
No. The supported mechanism is Android’s own VPN slot and works on any phone running Android 8.0 or newer.
Almost always cache: blocking the network does not empty what an app has already downloaded. Cast, local playback and anything else that does not use the internet also keep working.
Turn on auto-start on boot in Settings, and set NetCage as an always-on VPN in Android’s own settings, so the cage is up before your apps start.
No, and it is not built to. NetCage blocks whole apps, not requests inside them, so there is no domain filtering, no hosts file and no DNS interception anywhere in it. If an app is online, everything in that app is online.
Very little. The tunnel does no encryption, contacts no server and sends nothing — it reads packets from caged apps and discards them, which is close to the cheapest thing a VPN service can do. What costs battery is a VPN that forwards traffic, and NetCage forwards none.
No. Every feature works signed out, on the phone alone. Signing in with Google only copies your configuration to your other phones, and you can delete the account and its data at any time from Settings or from the deletion page on this site.
The documentation site covers setup, profiles, schedules, widgets and the limits.