Note

The options below are known to work on Android 14 / Samsung One UI 6.

Samsung DeX (the desktop mode available on higher-end Samsun Android smartphones) can be used with a limited number of (fairly standard) resolutions out-of-the-box. It is possible to use DeX with other resolutions however.

Good Lock

Samsung provides a application, Good Lock, that unlocks a number of customizations for Samsung’s version of Android. The MultiStar plugin can be used to enable additional display resolutions under DeX by turning on I ❤️ Samsun DeX → High resolutions for external displays.

ADB

The resolutions unlocked by Good Lock will work on the vast majority of modern display. However, occasionally you may want to use a monitor with an “oddball” resolution (like the 2240 × 1400 resolution used by the Lenovo ThinkVision M14d). The Android Debugging Bridge (adb) utility can be used in many of these cases.

Initial setup

1. Install F-Droid.
2. Install Termux.
3. Install adb: pkg install android-tools
4. Enable wireless debugging by turning on Developer options → Wireless debugging.
5. Select “Pair device with pairing code”. Note down the pairing code and port displayed in the resulting pop-up. (Note that this port is different than the debugging port!)
6. Pair adb in Termux with the phone: adb pair localhost:$PAIRING_PORT.

Setting a custom resolution

1. Enable wireless debugging (if it’s not already enabled from the previous section) by turning on Developer options → Wireless debugging. Note down the port displayed under “IP address & Port”.
2. Connect adb: adb connect localhost:$DEBUGGING_PORT
3. Use adb to set the resolution of your external display: adb shell wm size 2240x1400 -d 2
4. Disconnect adb: adb disconnect
5. Disabled wireless debugging.

Tip

In general, the Android phone itself will use display 0. To determine the number of the external display, you can output the current resolution of a display using adb shell wm size -d #, where # is 0, 1, 2, …

Warning

The display resolution set with adb shell wm size will stick until either a new display resolution is set using adb, adb shell wm size reset -d2 (or whatever the correct display number) is run, or until a new resolution is manually chosen in the Settings app under Samsun DeX → Display resolution.

Automatic resolution switcher script

The script below should (perhaps with minor modifications) automatically set DeX’s resolution to the optimal one for your external monitor.

Prerequisites

1. Turn on Developer options → Quick settings developer tiles → Wireless debugging. This will enable you to quickly turn wireless debugging on and off.
2. Install Termux, android-tools, and then pair (your local) adb with your (local) device using the steps described above in “Initial setup”.
3. Grant Termux permission to read the Android system logs: adb shell pm grant com.termux android.permission.READ_LOGS
4. Reboot your device.

Switcher script

Note

Adapted from Set max resolution for external displays Tasker task.

#!/usr/bin/env bash
 
DISPLAY_NAME="HDMI Screen"
DISPLAY_NUMBER=2
 
# Exit on error
set -e
 
# Get local adb port
PORT=$(logcat -d | grep 'adbwifi' | tail -n 1 | sed 's/.* //')
 
# Locally connect to the wireless debugging port
adb connect localhost:$PORT
 
# Get the connected display's highest resolution
DISPLAY_RESOLUTION="$(adb shell dumpsys display | grep -m 1 "$DISPLAY_NAME" | awk -F' |=' '/width/ && /height/ {for(i=1;i<=NF;i++) if($i=="width") print $(i+1) "x" $(i+3)}' | tr -d ',' | sort -nr -k1,1 -k2,2 | head -n 1)"
 
# Set the resolution for DeX
adb shell wm size $DISPLAY_RESOLUTION -d $DISPLAY_NUMBER
 
# Disconnect adb
adb disconnect
 
# Notify the user
MESSAGE="$DISPLAY_NAME ($DISPLAY_NUMBER) set to $DISPLAY_RESOLUTION"
if [[ $(which termux-notification | wc -l) -gt 0 ]]; then
        termux-notification --icon monitor --title "Samsung DeX" --content "$MESSAGE"
fi
echo "$MESSAGE"

Note

This will (often) generate a popup asking you to confirm log access when run.

Important

There is unfortunately no way to enable local adb in non-rooted devices without a WiFi connection.

Warning

On-screen text will sometimes look terrible after switching resolutions for some combinations of cables/monitors, even when the same device/cable/monitor works fine on a different combination!