Android Drops Wi-Fi When the Screen Turns Off

You unlock the phone and five notifications land at once. A file transfer that was halfway through has not moved. The smart plug you scheduled did not respond until you woke the screen.

What is happening is almost certainly not a disconnection. Android suspends the Wi-Fi radio into a low-power state when the screen goes off, keeping the association alive while batching traffic into brief wake windows. That is by design and it saves a meaningful amount of battery. The problem is when the suspension is more aggressive than you want, or when something turns it into a genuine drop.

Suspended and disconnected are different problems

Work out which one you have before changing anything, because the fixes do not overlap.

A phone that reconnects in two seconds when you wake it was disconnected. A phone already showing full Wi-Fi bars the instant the screen lights was suspended. That one observation splits the guide in half.

The battery policy side

Android’s Doze mode is the main mechanism. With the screen off and the device stationary for a while, the system stops apps from waking whenever they like and collects their network work into periodic maintenance windows. The deeper the doze, the further apart those windows.

High-priority push messages are supposed to break through this, which is why messaging apps generally still work while everything else waits. When they do not, it is because that app has been restricted.

Set the affected app to Unrestricted. On stock Android, Settings → Apps → [app] → App battery usage → Unrestricted. On Samsung and other skins the same control sits in the battery section of the app’s info page, labelled differently. Grant it to the apps whose background network work you genuinely need and leave the rest optimised, because exemptions are not free.

On Samsung there is a second layer. The battery settings include lists of sleeping and deep sleeping apps that override the per-app setting, and apps get added to them automatically after a period of disuse. An app in the deep sleeping list will not use the network in the background no matter what you set elsewhere. The full picture of OEM background killing covers Xiaomi and OnePlus too, which are more aggressive again.

Also check Adaptive Battery if a single app is persistently affected and others are not. It learns usage patterns, and an app you open rarely gets progressively less background time whether you want that or not.

Stop the phone switching to mobile data

Most Android phones have a feature that moves you off Wi-Fi automatically when the connection looks poor, and it is a common cause of “Wi-Fi drops when idle” — the phone did not lose Wi-Fi, it decided mobile data was better while you were not watching.

Look in Settings → Network & internet → Internet → Network preferences on stock Android for the option to switch to mobile data automatically, and turn it off. Samsung’s equivalent sits in the advanced area of the Wi-Fi settings, as does its adaptive Wi-Fi feature, which does much the same thing.

If this was the cause you will usually notice something else first: unexpected mobile data usage overnight. That is a useful confirming signal.

Then look at the router

If the phone genuinely disconnects and has to re-associate, the phone is often not the interesting half of the problem.

Band steering. Routers that present one network name across 2.4GHz and 5GHz decide which band each client uses. A dozing phone with a weakened signal gets pushed between bands, and each handover is a brief disconnection. Splitting the bands into two separate network names and joining the 5GHz one explicitly stops it dead, at the cost of managing two names.

Short DHCP leases. If the router hands out leases measured in minutes, a phone in deep doze can miss its renewal and lose its address. Lease time lives in the router’s LAN or DHCP settings; raising it to 24 hours removes the issue entirely.

Idle client timeouts. Some routers disconnect clients that have been quiet for a set period — exactly what a dozing phone looks like. Business-class and mesh systems are the ones that tend to ship this enabled.

Scheduled reboots. Many routers restart themselves nightly. If your drop happens at 3am every night without fail, stop investigating the phone.

Interference and distance. A phone on a nightstand two rooms from the router sits at the edge of usable signal, and marginal signal plus power-save mode is where connections fail. The broader version of this is covered in Wi-Fi that keeps disconnecting, and if the symptoms extend to full bars with nothing loading, connected but no internet is the right starting point instead.

The settings on the phone worth changing

A short list, in order of how often they matter.

1. Wi-Fi scanning off. Under the location settings, the phone scans for networks even when Wi-Fi is off. It wakes the radio periodically and gains you only slightly better location accuracy.
2. Forget and rejoin the network. This clears a stale DHCP lease, a cached gateway and any saved proxy in one step. Have the password ready.
3. Static IP as a test. In the network’s settings, switch IP settings from DHCP to Static and assign an address outside the router’s DHCP pool. If drops stop, the problem was lease renewal and you have confirmed it.
4. Turn off Private DNS temporarily. A private DNS hostname that becomes unreachable produces a connection that is associated but useless, which reads as a drop. Settings → Network & internet → Private DNS → Off, as a test.
5. Randomised MAC off for this network. Some routers with MAC-based rules or device limits handle rotating addresses badly. It is in the network’s own settings page, under privacy.

Keep the download alive

If the specific complaint is that transfers stall, the mechanism is different again.

An app that declares a foreground service and shows a persistent notification keeps running with the screen off. An app that does not is suspended, and its download waits. This is why the Play Store, a podcast app and a proper download manager all continue while a browser download sometimes does not.

Two practical workarounds: use the app’s own download feature rather than a browser where one exists, and keep the screen on with the phone plugged in for large transfers. Developer options include a Stay awake while charging toggle that is made for this.

What does not help

• Wi-Fi keep-alive and signal booster apps. They cannot override the radio’s power-save behaviour, which is implemented below the level any app reaches. What they can do is hold a wakelock all night, which costs you battery and fixes nothing.
• Turning Wi-Fi off at night. The phone falls back to mobile data, which uses more power in a weak-signal bedroom, and keeps scanning anyway unless you disable Wi-Fi scanning separately.
• Resetting network settings as a first step. It wipes every saved network, VPN and Bluetooth pairing. Worth trying eventually, not first.
• Disabling battery optimisation for everything. You will fix the symptom and acquire a far worse overnight drain problem in its place.

Realistic expectations

If the cause was adaptive switching to mobile data, turning that off fixes it immediately and permanently. If it was battery optimisation on one app, setting that app to Unrestricted does the same.

The honest limit is that you cannot make Android keep the Wi-Fi radio fully awake all night, and you should not want to. Doze is why phones last as long as they do on standby. What you can do is exempt the two or three apps that matter and stop the phone wandering off to mobile data behind your back. Everything else arriving in a batch when you unlock is the system doing its job.