Samsung DeX turns your Galaxy S25 Ultra into a powerful desktop experience, allowing you to use apps, files, and multitask on a larger display. But if DeX fails to connect to your monitor, it can be frustrating, especially when you rely on it for work or productivity.
Most connection issues are caused by faulty cables, incompatible monitors, or incorrect DeX settings. Let’s go over the best ways to fix it and get DeX running smoothly again.
Why Your Galaxy S25 Ultra DeX Might Not Be Connecting
- The HDMI cable or USB-C to HDMI adapter is faulty.
- The monitor’s input source is set incorrectly.
- DeX mode is disabled or not launching automatically.
- Software bugs or outdated firmware.
- The monitor does not support the required HDMI protocol.
Check the Cable and Adapter.
DeX requires a high-quality USB-C to HDMI adapter or cable that supports video output. Using low-quality or non-certified cables often prevents proper connection.
- Disconnect the USB-C cable, and then inspect both ends for damage or dirt.
- Try another Samsung DeX-compatible HDMI cable or adapter, and reconnect it to the monitor.
If possible, test the adapter with another device that supports HDMI output to confirm that it works correctly.
Verify the Monitor Input Source.
Sometimes, the problem is as simple as the monitor being set to the wrong input. DeX will not show unless the correct HDMI input is active.
- On your monitor, press the Input or Source button.
- Choose the HDMI port your Galaxy S25 Ultra is connected to, and wait a few seconds.
Once the correct input is selected, DeX should automatically appear on your monitor.
Enable Samsung DeX Manually.
If DeX does not launch automatically when you connect your phone, you can turn it on manually from your settings.
- Swipe down from the top-right corner to open Quick Settings.
- Tap the DeX icon, and then choose “Start Samsung DeX on connected display.”
If you do not see the icon, open Settings, tap Connected devices, then tap Samsung DeX, and enable it from there.
Restart Both Devices.
Minor software conflicts or temporary glitches may stop DeX from initializing. Restarting both your phone and the monitor often fixes this.
- Swipe down from the top-right corner, tap the Power icon, and then tap Restart.
- Turn off your monitor, wait 10 seconds, then power it back on.
After both devices restart, reconnect the cable and check if DeX appears.
Update Software and Firmware.
Keeping your Galaxy S25 Ultra and monitor up to date ensures the best compatibility with DeX.
- Open Settings, and then tap Software update.
- Tap Download and install to check for new updates.
If your monitor supports firmware updates, visit the manufacturer’s website to update it as well.
Try Wireless DeX.
If DeX still will not connect using a cable, try using Wireless DeX instead. This can confirm whether the issue is hardware-related.
- On your Galaxy S25 Ultra, open Settings, then tap Connected devices.
- Tap Samsung DeX, and then select “DeX on TV or monitor.” Choose your compatible wireless display from the list.
Make sure both devices are connected to the same Wi-Fi network.
If DeX launches successfully this way, your wired adapter or cable may need replacement.
Once these steps are done, DeX should connect seamlessly and display your phone’s desktop interface on the monitor. With a reliable setup, you can enjoy a PC-like experience powered entirely by your Galaxy S25 Ultra.
FAQs
What type of HDMI cable do I need for DeX?
Use a USB-C to HDMI cable or adapter that supports DisplayPort Alternate Mode. Samsung’s official DeX cable or adapter is recommended for stable performance.
Can I use DeX with any monitor?
Most modern monitors work with DeX, but some older models may not support the required HDMI protocol or resolution. Try testing another display if DeX fails to load.
Why does my DeX connection keep disconnecting?
This can happen due to a loose cable, overheating, or background apps consuming system resources. Use a high-quality cable and keep your phone cool for better stability.
