Floating overlays
on Android — explained.

Android has a permission that most users have never intentionally used, even though they've seen its effects. It's called SYSTEM_ALERT_WINDOW — labeled "display over other apps" in your Settings. It lets an app draw a window that appears on top of every other app running on your phone.

This guide explains what it is, how it works, which apps use it, and what becomes possible with it.

What display over other apps actually means

Normally, Android apps are sandboxed. When you're in Gmail, Gmail fills your screen. Instagram can't draw on top of Gmail. Your camera can't overlay anything on your maps app. Each app exists in its own window, and the system manages which one is visible.

SYSTEM_ALERT_WINDOW breaks this rule — with your permission. An app that has this permission can draw a window that sits above everything else in the system's z-order. The window can be any size, any shape, anywhere on screen. Other apps remain interactive underneath it.

This is how chat heads worked. This is how screen recorders show their floating record button. This is how accessibility apps display reading assistance over web pages. And this is how Bubbles In Time keeps your photos visible over everything you do.

How to grant the permission

Unlike most Android permissions, SYSTEM_ALERT_WINDOW can't be granted with a simple dialog box. Android requires users to explicitly navigate to Settings to enable it. This is intentional — Google added this friction because the permission is powerful and was being abused.

When BIT prompts you to enable floating bubbles during onboarding, it opens the relevant Settings screen directly. You flip a toggle. You're done. The permission is granted once and persists until you revoke it.

To check or revoke it at any time: Settings → Apps → Special app access → Display over other apps.

What happens when the overlay is active

When an app is drawing a floating overlay, Android shows a persistent notification. This is also intentional — Android's policy requires that users always know when an overlay is active. BIT shows this notification whenever the bubble service is running.

The notification can't be dismissed while the service is active, but it can be minimized. You can stop BIT's overlay at any time by dismissing the notification or toggling the service off inside the app.

Common apps that use this permission

• Facebook Messenger — chat heads (currently optional, toggle in Messenger settings)
• Screen recorders — floating record/stop button
• Accessibility apps — text magnification, reading assistance layers
• Floating calculators and note apps — small utility windows
• Bubbles In Time — floating photo, video, and memory bubbles

Battery impact and performance

A floating overlay requires a foreground service — a persistent background process Android keeps alive. This has a small but real battery impact. In testing, BIT's impact is minimal between bubble events. The brief moment when a bubble renders and animates uses a small CPU spike.

On modern Android devices the impact is negligible. On older or lower-end devices, aggressive battery management settings may affect how reliably the service runs. See our device compatibility guide for specific notes on Samsung, Xiaomi, and other manufacturers known for aggressive battery optimization.

Android versions and compatibility

SYSTEM_ALERT_WINDOW has existed since Android 1.0, but the way it's granted and managed has changed significantly over the years. BIT targets Android 8.0 (API 26) and above, which covers the vast majority of active Android devices and ensures consistent permission behavior.

Android 14 introduced additional foreground service restrictions that BIT's v4 build handles correctly with the FOREGROUND_SERVICE_SPECIAL_USE declaration. Read more about BIT's technical compatibility.

The bigger picture: what overlays enable

The floating overlay permission is one of the most powerful and underused capabilities in Android. Most apps that have it use it for utility — calculators, notes, screen capture controls. Very few use it for something emotionally meaningful.

BIT's bet is that the overlay layer — the surface that exists above all other apps — is the right place for things that matter to you personally. Not utilities. Not notifications. Memories, people, moments. The things you want present without having to go looking for them.

That's a different use of the same technical capability. And it turns out to feel meaningfully different when you experience it.