Why a Blocked App Might Reopen on Its Own on an Android Phone

If an app you blocked is back within a day, the block probably didn't fail. Most Android phones, especially from Xiaomi, Realme, Oppo, and Vivo, aggressively kill background apps to save battery, and any blocking tool that isn't specifically exempted from that can get shut down without you knowing.

Why does a blocked app work for a while and then start opening again?

Because Android phones, especially ones running heavily customized software, treat a blocking tool's background service as something safe to kill once the phone decides it needs to save power. Nothing about the block itself failed. The process that enforces it just got shut down quietly, usually after the phone's been idle for a while or the battery dropped below a certain point. From the outside it looks identical to the block simply not working, which is why most parents assume the app is broken rather than the phone's own power management doing exactly what it was built to do.

Which phones are most likely to do this?

Xiaomi's MIUI, Realme's software, Oppo's ColorOS, and Vivo's Funtouch OS are the most aggressive about it, because each brand runs its own battery management layer on top of Android that goes further than stock Android does. Samsung and stock Android phones, like Pixel, do less of this by default, though even those can still kill a background app under a strict battery saver mode. If the same block keeps failing on one phone in the house but never on another, the phone's brand is usually the actual variable, not the app.

How do I check whether this is actually happening on my phone?

Open your phone's battery settings and look for the app under something like "battery optimization," "app battery usage," or "background restrictions," depending on the brand. If it isn't already set to "unrestricted" or "no restrictions," that's the likely cause. A separate setting, usually called "autostart" or "auto-launch" and tucked into app permissions or a "manage apps" section, needs to be turned on too, since some phones kill an app on restart unless it's specifically allowed to start itself back up. Checking this by hand every few weeks is tedious, which is exactly the gap a built-in self-check closes: CrenelView shows directly on its own screen whether blocking is actually active on your specific phone, instead of leaving you to dig through settings to find out.

How do I fix it once I know which setting is the problem?

Set battery optimization for the app to "don't optimize" or "unrestricted," and turn autostart on if your phone has that setting. On most phones both live inside Settings, then Apps, then the specific app, though the exact wording and menu depth varies by brand. Restart the phone once after changing both, since some manufacturers only apply the new permission cleanly after a restart rather than immediately.

Is there a way to know for sure the block is still active, without checking settings every time?

Worth looking for a blocking tool that tells you this directly rather than assuming your settings will hold forever, since a routine phone update can quietly reset both permissions without any notice. CrenelView runs that check inside the app itself and tells you plainly whether blocking is active on your specific phone right now, rather than leaving you to find out only when your child is already back in a game that should have stayed closed.

Check autostart and battery optimization once after any phone update, since that's usually when a working block quietly stops.