Deskbridge › Guides › Secure Blackout
Keep your phone's screen off while using DeX (without freezing it)
Don't use the power button: a sleeping Galaxy freezes DeX, and a locked one hides the DeX dock and blocks typing. Instead, keep the phone awake behind a pure-black screen — on OLED that looks exactly like “off.” Deskbridge's Secure Blackout does this and locks the phone the instant anyone touches it or you unplug.
The problem: two Android rules collide
Rule 1: a sleeping phone pauses DeX
When your phone sleeps (Android calls it doze), the DeX display on your Mac stops responding. The power button causes it; so does switching the panel off through the system — scrcpy's --turn-screen-off option sends Samsung phones into doze too. (Details in our scrcpy guide.)
Rule 2: a locked phone shrinks DeX
DeX keeps running behind the lock screen, but Samsung strips the dock down to bare navigation buttons — no apps, no clock — and blocks typing until you unlock. That's deliberate: otherwise anyone could use your phone's apps from the desktop.
So the obvious ways to “turn the phone off” either freeze DeX or cripple it.
The fix: black, awake, and protected
Secure Blackout keeps the phone awake and unlocked but covers its screen with pure black at zero brightness. On the OLED screens every recent Galaxy uses, black pixels emit no light, so the phone looks and feels off on your desk. Meanwhile DeX keeps its full dock, keyboard and apps on your Mac.
| What happens | Result |
|---|---|
| Someone touches the phone | Locks instantly |
| You unplug the cable | Locks instantly |
| You close DeX or quit Deskbridge | Locks instantly (never left unlocked) |
| The phone was already locked | A tap reveals the lock screen so you can unlock |
| Someone presses the power button anyway | Deskbridge wakes the phone so DeX doesn't freeze |
Turn it on
- Open DeX with Deskbridge (it opens when you plug in — see setup).
- Unlock your phone once.
- Choose Black Out Phone Screen in the Deskbridge menu, or press ⌥⌘B. To make it automatic, turn on Black Out Phone Screen Automatically.
To lock itself instantly, Deskbridge's small phone helper uses Android's device-admin permission limited to locking the screen — nothing else. You can revoke it in your phone's Settings.
Unlock from your Mac
If the phone did lock — after a touch, a call or the power button — you don't have to pick it up. Press ⌥⌘U (Unlock Phone…), type your PIN or password on your Mac keyboard, and Deskbridge enters it on the phone. It's sent straight over the cable and never stored. Pattern lock? Touch the fingerprint sensor instead (on Galaxy foldables you can do that without opening the phone). The full dock and typing come straight back.
FAQ
Why does DeX freeze when I turn off my phone's screen?
Turning the screen off with the power button puts a Galaxy phone to sleep (doze), and a sleeping phone pauses the DeX display. Tools that switch the screen off via the system, like scrcpy's --turn-screen-off, cause the same doze on Samsung phones.
Why does the DeX dock lose its apps when my phone is locked?
That's Samsung's security: while the phone is locked, DeX shows only navigation buttons and blocks typing, so nobody can use your apps from the desktop. Unlocking brings the full dock back.
How does Secure Blackout keep the phone dark?
It keeps the phone awake and unlocked behind a pure-black screen at zero brightness. On an OLED screen black pixels are off, so it looks off — and DeX keeps its full dock.
Is my phone left unlocked?
Only behind the black screen. Touch it, unplug it, close DeX or quit Deskbridge and it locks instantly.
What if my phone is already locked?
Press ⌥⌘U on your Mac and type your PIN or password. Deskbridge enters it on the phone and never stores it. Fingerprint unlock on the phone works too.
Phone screen off. DeX on.
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