If your phone’s Wi-Fi works while you’re using it and drops once the screen locks, the cause is one of three things: your router, your phone’s power saving, or an app such as a VPN. You can tell which with two quick tests, and neither takes more than ten minutes. The phone dropping Wi-Fi while mobile data keeps working is not a sign that the phone is broken, which is why people go round in circles resetting settings before they find the cause.
Test One: The Second-Device Test
Leave a second device, like a laptop, tablet, or another phone, connected to the same Wi-Fi network and idle for the same amount of time your phone takes to drop. Keep the screen locked or asleep on it too, and then check whether it’s still connected.
If the second device also loses its connection or loses internet, your phone isn’t the problem. Look at the router. Apple’s Wi-Fi guide suggests checking whether other devices can join, trying the 5 GHz band instead of 2.4 GHz if your router offers both, power-cycling the router and modem, and updating the router’s firmware. A router that’s far away, overloaded, or running old firmware often drops idle devices first.
If the second device stays connected, the router is probably fine and the problem is on your phone. Go to the next test.
Test Two: The Plug-In Test
Phones save battery by letting the Wi-Fi radio sleep when the screen is off, and different phones and settings are more aggressive than others. This test shows whether power saving is the cause.
Plug the phone in and turn off Low Power Mode or Battery Saver. Lock the screen and wait as long as it usually takes for the drop to happen. Then unplug it, turn power saving back on, and repeat.
If the Wi-Fi stays connected while charging and drops on battery, or drops only with power saving on, then power management is the cause. iPhone owners in Apple’s community threads describe the same pattern, and some replies there say an idle iPhone behaves differently when it’s plugged in. Turn off the power-saving mode, or look for a setting that lets Wi-Fi stay on during sleep. Lenovo’s own support page for Wi-Fi that disconnects when the screen is off puts turning off battery saver or a third-party battery manager first. On many Samsung phones, Samsung Community posters also point to Wi-Fi power saving or battery optimization settings and the “Keep Wi-Fi on during sleep” option on older versions. Menus differ by brand and Android version, so search your settings for “Wi-Fi” under battery or connections.
If the Wi-Fi drops even while plugged in with every power-saving mode off, move to the third test.
Test Three: Does It Happen on Other Networks and Without Apps?
Connect your phone to a different Wi-Fi network, such as a friend’s or your phone’s hotspot on another device, and repeat the lock-and-wait test. If it only happens on your home network, but other devices stay connected, the router and your phone may not be getting along, and trying the 5 GHz band or restarting the router is worth doing again.
If it happens on every network, the cause is in the phone. Apple’s guidance includes turning off Airplane Mode and Connectivity Assist, and removing any VPN or security software, then restarting and testing again. If the Wi-Fi stays connected afterward, the app was the cause. As a last step, Apple says to reset network settings, which also removes saved networks and passwords, so use it only after everything else has failed.
Why Mobile Data Staying On Is Normal
When Wi-Fi drops with the screen off, many phones switch to mobile data without telling you, so messages and notifications keep arriving. That behavior is by design. If you also see “No SIM” or “No Service,” that’s a separate issue, and this guide on intermittent SIM errors covers it. If Wi-Fi shows as connected but pages won’t load, the symptom is closer to a hotspot that connects with no internet, where the connection exists and the data doesn’t flow.
What About Battery?
Keeping Wi-Fi awake uses more power than letting it sleep, so turning off a power-saving setting can cost you some battery. If you notice your percentage jumping around afterward, this guide to sudden battery drops explains how to tell a normal reading from a worn battery.
FAQ
Why does my phone’s Wi-Fi turn off when the screen is locked?
The usual causes are a power-saving mode that lets the Wi-Fi radio sleep, a router that drops idle devices, or a VPN or security app. A second-device test and a plug-in test show which one it is.
How do I stop Wi-Fi from disconnecting when my phone sleeps?
Turn off Low Power Mode or Battery Saver, look for a Wi-Fi power-saving or battery-optimization setting in your phone’s settings, and check your router by seeing whether a second idle device also drops.
Is it normal for Wi-Fi to disconnect while the phone is idle?
Some power-saving behavior is normal, but a connection that drops every time the screen locks, while other devices stay connected, usually points to your phone’s power settings or an app.
Why does my phone switch to mobile data when the screen is off?
When Wi-Fi drops or sleeps, many phones fall back to mobile data so notifications keep arriving. That behavior is usually deliberate, not a fault.
Should I reset my network settings to fix Wi-Fi dropping?
Only as a last step. A network reset deletes saved Wi-Fi networks and passwords, and it doesn’t fix problems caused by a router, a VPN, or power-saving settings.