VPN keeps disconnecting on Android: causes and fixes

A VPN that keeps disconnecting on Android nearly always has one of five causes: the battery optimiser is killing the VPN service, the phone is switching networks, the connection is timing out while idle, the network you are on is interfering with the tunnel, or the provider's session limit is being reached. Each has a distinct pattern, and reading the pattern tells you which fix to try first.

Read the pattern before changing anything

The timing of the drops is the most useful clue you have.

Battery optimisation is killing the service

Android stops background work it believes is idle, and a manufacturer's own power manager can be far more aggressive than Android's. A VPN service looks idle whenever you are not actively moving data, so it is a prime target. The pattern is a drop shortly after the screen goes dark, and a reconnect when you pick the phone up.

The fix is to tell Android the app is exempt. Under the app's battery settings, choose the unrestricted option. On phones from some manufacturers there is a second layer, sometimes called auto-start, app launch management or protected apps, that also needs the VPN allowed. Turning on Always-on VPN for the app helps as well, because Android then restarts the tunnel itself rather than waiting for the app. Stopping the battery optimiser from killing your VPN and keeping a VPN alive on Samsung and Xiaomi phones go through the exact menus.

The phone switched networks

When the phone moves from Wi-Fi to mobile data, or between two Wi-Fi networks, its address changes and any connection tied to the old address breaks. Modern VPN protocols are built for this: WireGuard recognises the same client from a new address and carries on, and IKEv2 has the same capability. What you should see is a pause of a second or two and then normal service. What you should not see is a full disconnect with a fresh handshake every time. If you do, the app is treating a roam as a failure, and the only fix is an app that does not.

The connection timed out while idle

Mobile carriers, and most home routers, translate addresses, and they forget an idle connection after some time so they can reuse the slot. If the VPN sends nothing for long enough, the path closes and the next packet from the server has nowhere to go. A well-built app sends a small keepalive often enough to prevent this, typically every 25 seconds or so, and lets the radio sleep in between. If your VPN survives while you are using the phone and is dead when you come back to it, the keepalive is too rare or is being suppressed by battery optimisation, which brings you back to the section above.

The network is interfering

Some Wi-Fi networks in hotels, campuses and offices filter VPN protocols or drop UDP traffic, and some do so unevenly: the tunnel comes up, works for a while, then dies. The pattern is drops on one network and stability everywhere else. A well-built app tries several connection methods and keeps the one that works on that network, and the one that survives on a restrictive network is often a TLS-wrapped transport on TCP port 443. It is slower, but it holds. What to do when the Wi-Fi blocks VPN connections covers this in detail.

The session reached its ceiling

Providers cap how long a single session may run, partly so that a server can be drained and maintained without stranding anyone for days. Culvert VPN sessions have a 24-hour ceiling, and the app reconnects automatically when it is reached; a single short drop at roughly the same time each day is that ceiling working as designed. Why VPN sessions expire and reconnect explains the reasoning.

The server is unhealthy

If the drops are random, happen on every network and come with slow speeds beforehand, the server may be overloaded or failing. A good app monitors this and moves you, but if yours does not, switching to a different city is the quickest test. If a different city is stable, the first one was the problem.

A short checklist, in order

1. Note when the drops happen and match the pattern to the table above.
2. Exempt the VPN app from battery optimisation and any manufacturer power manager.
3. Turn on Always-on VPN for the app in Android's VPN settings.
4. If drops happen on only one Wi-Fi network, accept that the app may need a slower transport there.
5. If drops are random on every network, try a different city.

Culvert VPN keeps a WireGuard tunnel across Wi-Fi and data switches, sends keepalives on a schedule that survives carrier timeouts, tries several connection methods on restrictive networks and reconnects automatically at the 24-hour ceiling; it is free on Google Play.