REX TechnologiesAndroid Headless Mirror

Guide

How to.

Step by step, for the things people do most. Each recipe ends with the keys and the settings involved.

Connect your phone the first time

Once only. After this the mirror opens by itself whenever the phone is plugged in.

  1. Install the app and open it. The window shows the phone side step by step.
  2. On the phone, open Settings → About phone and tap Build number seven times.
  3. Open Developer options and turn on USB debugging.
  4. Plug the phone in with a cable that carries data. Unlock it, tick Always allow from this computer and tap Allow.
  5. The mirror opens and the phone's own screen turns off. Tap its power button any time to use it in your hand.
Settings
Open the window when a phone connects, Phone screen off while mirroring

Go fullscreen and keep the controls

Fullscreen fills the whole display; the controls shrink to a small bar you place yourself.

  1. Press F11.
  2. Move the pointer: the controls fade in. Drag the bar by its dotted grip to wherever suits you.
  3. Leave it alone and it fades. Move the pointer back to where you left it and it returns.
  4. Press Esc to put the window back.
Keys
F11, Esc
Settings
Fullscreen controls

Zoom in and move around

Zoom scales the picture on this PC; the phone does not know.

  1. Hold Alt and turn the mouse wheel, or pinch with two fingers on the touchpad.
  2. Hold Alt and drag, or slide two fingers, to move around.
  3. Drag the frame in the navigator to jump to another part of the screen.
  4. Ctrl+Alt+0 fits the phone to the window again.
Keys
Alt + wheel, Alt + pinch, Alt + drag, Ctrl+Alt+0
Settings
Zoom & navigator

Keep the phone's music quieter than the PC, or mute it from anywhere

This changes the phone's sound on this PC only; the phone's own volume stays where it is.

  1. Click the sound button in the top bar and drag the slider. The level is kept for this phone.
  2. Or press Ctrl+Alt+PageDown and Ctrl+Alt+PageUp; Ctrl+Alt+Shift+M mutes and unmutes.
  3. To mute it from any app, open Settings → Shortcuts from anywhere, choose Mute on this PC and give it a key.
  4. For quiet while you work, turn on Mute while another window is in front in Settings → Sound on this PC.
Keys
Ctrl+Alt+PageUp, Ctrl+Alt+PageDown, Ctrl+Alt+Shift+M
Settings
Sound on this PC

Open an app from the PC, and keep favourites on keys

The list comes from the phone itself the first time it is mirrored; Read again fetches it after you install something.

  1. Press Ctrl+Alt+2 for the Apps tab, or click Apps in the side panel.
  2. Start typing a name: the list narrows as you type. Enter or a click opens the app; Shift opens it fresh.
  3. Click the star beside an app to make it a favourite. Favourites have tiles at the top of the Controls tab.
  4. Press Ctrl+Alt+Shift+1 for the first favourite, up to Ctrl+Alt+Shift+9. Move them up and down from their menu to change which key opens which.
Keys
Ctrl+Alt+2, Ctrl+Alt+Shift+1 to 9
Settings
Apps

Send files, folders or an app to the phone

Files go only into the phone's shared storage. APK files are installed instead of copied when that setting is on.

  1. Drop files or a folder onto the window, or choose Send files… in Controls.
  2. To reuse File Explorer's clipboard, copy the files and press Ctrl+Alt+V.
  3. If an APK or a large batch needs approval, check the question and choose Install or Send.
  4. Watch the item in Controls. Cancel stops its own ADB process and removes a partial copy; Try again puts it back in the queue.
Keys
Ctrl+Alt+V
Settings
Sending files
Command line
rex push, rex install

Watch a video beside a chat, or use an app at PC size

The second screen is one app on a display of its own. It needs Android 10 or later.

  1. In Controls, choose Open an app on a second screen…, then pick the app in the Apps tab. Or press Ctrl+Alt+D.
  2. Click the view you want to use: keys and Home, Back and Recents go to it, and an outline shows which it is.
  3. Drag the splitter between them to share the space differently; double-click it to put it back.
  4. For the phone's screen to stay dark while the app runs here, choose Instead of it in the same section.
  5. Switch app… puts another app on the same screen; Close it moves the app back to the phone.
Keys
Ctrl+Alt+D
Settings
Second screen & views

A profile for games, and one that switches on by itself

A profile holds only the settings you put in it, so applying one never undoes the rest.

  1. Set the mirror up the way you want it for games: frame rate, bit rate, sound.
  2. In Settings, Profiles, choose Save the current settings as a profile…, name it Gaming, and keep only the groups it is about.
  3. Apply it from its card, from the tray's Profiles menu, or with Ctrl+Alt+F1 while it is first in the list.
  4. To have it on whenever you go fullscreen, choose it under In fullscreen use. Leaving fullscreen puts back what it changed.
  5. On a laptop, On battery use can pick Battery saver the same way.
Keys
Ctrl+Alt+F1 to Ctrl+Alt+F9
Command line
rex profile apply Gaming
Settings
Profiles

Keep only the buttons you use

The Controls tab can hold just what you reach for, in your order.

  1. In Settings, open Controls tab.
  2. Turn off the sections you never use, and move the others with Up and Down.
  3. Take tiles out of a grid with Remove, or pick any action under it and choose Add.
  4. Choose how many tiles a row has, and whether they show their names.
  5. For the top bar, open Window: tick the phone buttons it keeps, and under More buttons in the top bar pick any other action and choose Add.
Settings
Controls tab, Window

Use your own keys

Any action can have a key, and any key can be moved.

  1. In Settings, open Keyboard shortcuts, or type the action into Find a setting.
  2. Click its box and press the keys. A key needs Ctrl, Alt or Win, or is F1 to F24 on its own, so typing into the phone never sets it off.
  3. Backspace takes a key away; Put back returns the one it shipped with.
  4. From the command line: rex keys set home Ctrl+Alt+J.
Settings
Keyboard shortcuts

Make the window as small and quiet as it can be

Only the phone, at the size it is.

  1. In Settings, Window, turn off Top bar and Status bar. Ctrl+Alt+B still hides and shows the side panel.
  2. Press Ctrl+Alt+F to fit the window to the phone, or turn on Fit the window to the phone as the mirror starts.
  3. Make the side panel's text larger or smaller with Side panel size when you open it.
Settings
Window

Record a demo of an app

Show where you tap, keep the picture still however the phone is held, and stop on time.

  1. In Settings, Picture, turn on Show taps on the phone, and set When the phone turns to It stays upright.
  2. To show one part of the screen only, type it into Show only part of the screen as width:height:x:y in the phone's pixels, then press Enter.
  3. In Phone screen & session, choose how long under Stop the mirror after.
  4. In Screenshots & recording, turn on Record every session, then choose Restart now in the bar that offers it.
Settings
Picture

See what you changed, and put any of it back

Every setting the app keeps is in the Settings tab, so nothing needs editing by hand.

  1. In Settings, choose Changed beside the search box. It lists every setting that is not as the app ships, with its value now.
  2. Put back beside one returns just that setting; Put them all back returns every one, after asking.
  3. Click a setting's name to find it where it lives.
  4. At the end of any group, Put this group back to how it ships does the same for that group only.
Settings
Every setting explained

Use a work phone and a personal phone together

Both phones need USB debugging allowed, as for one.

  1. Plug in the second phone while the first is mirrored. The notice bar asks whether to show it beside; choose Show it beside.
  2. Click a phone's picture to use it: the strip above the tabs says which phone the tabs act on. Ctrl+Alt+O switches.
  3. From the phone menu at the top, make the one beside the main phone, or stop showing it.
  4. To hear only the phone you are using, set Sound on this PC from to The phone you are using.
Keys
Ctrl+Alt+O
Command line
rex phones
Settings
Second phone

Type, and browse a feed without the mouse

Typing goes to the phone as it would from a plugged-in keyboard.

  1. Click the phone's picture, then type. Digits, symbols and AltGr work in your phone's keyboard layout.
  2. To scroll a feed with the keyboard, press Ctrl+Alt+K: browse mode is on.
  3. Use Down and Up for the next and previous item, Enter to tap, L to like, M to mute and Backspace to go back.
  4. Press Esc to go back to typing.
Keys
Browse mode keys
Settings
Mouse, touchpad & keyboard

Bring the mirror up from anywhere, and give an action a key

These keys work while the window is hidden in the tray or behind other windows.

  1. Press Ctrl+Alt+M in any app: the mirror comes to the front, ready to type into. Press it again and it goes back to the tray.
  2. To choose another key, open Settings → Shortcuts from anywhere, click the box under Show or hide the window and press the keys you want. Backspace turns it off; Esc keeps the old one.
  3. To skip to the next video while you work, pick Next item under More shortcuts from anywhere, choose Add a shortcut… and press a key such as Ctrl+Shift+F9.
  4. Turn on Say what a shortcut did, from the tray to hear back while the window is hidden.
Keys
Keys from anywhere
Settings
Shortcuts from anywhere

See the phone twice or more

Copies are extra live views of the same phone, side by side.

  1. Hold the phone upright.
  2. Press Ctrl+Alt+N, or Add a copy in Controls. Repeat for more, as many as fit the window at full height.
  3. Touch, type and zoom in any of them.
  4. Ctrl+Alt+W closes the last copy.
Keys
Ctrl+Alt+N, Ctrl+Alt+W
Settings
Copies of the phone

Unlock a phone whose lock screen is black

Some phones protect their lock screen from being mirrored. The guide shows where the dots are.

  1. Lock the phone. The first time, the app asks what kind of lock it has; choose Pattern.
  2. The nine-dot guide appears over the black picture, where Android puts the dots.
  3. Draw your pattern over it with the mouse.
  4. If the dots are off, press Ctrl+Alt+C and line them up with the arrow keys.
Keys
Ctrl+Alt+P, Ctrl+Alt+C
Settings
Lock screen

Take screenshots and record

Screenshots are saved in full quality; recordings capture each session.

  1. Press Ctrl+Alt+S, or the camera in the top bar.
  2. The status bar names the file. Click the name to show it in File Explorer.
  3. To record every session, turn on Record every session in Settings.
Keys
Ctrl+Alt+S
Settings
Screenshots & recording

Fix a phone Windows will not read

When Windows binds the wrong driver or gives up reading the phone, the app notices within a few seconds.

  1. Leave the phone plugged in. The bar above the mirror offers Repair USB driver or Fix USB.
  2. Click it and approve the Windows administrator prompt once.
  3. To have it fixed without asking next time, choose Fix automatically from now on.
  4. Still nothing? Try a port on the PC itself rather than a hub, and another cable.
Settings
Fix USB by itself when Windows can't read the phone