Dell U2720Q Flickering on MacBook Pro? Fix It

Dell U2720Q flickers when connected to a MacBook Pro via USB-C. Here's the exact fix—it's not the cable, it's the monitor's firmware and a simple setting.

You're working on a MacBook Pro (2019 or newer, running macOS 12 or later). You plug in the Dell U2720Q via the USB-C cable that came in the box. At first, everything looks fine. Then, after a few minutes—or sometimes right away—the screen flickers. Not a full blackout, but a rapid, annoying brightness dip that happens every 10 to 20 seconds. It gets worse when the screen shows bright white backgrounds, like a word processor or a browser window.

I've seen this exact issue dozens of times in our office. The root cause isn't the cable, even though that's the first thing people blame. It's a combination of the monitor's firmware being old and a power management feature that Dell calls 'USB-C Prioritization.' When that feature is set to 'High Resolution,' the monitor negotiates too much bandwidth for the display signal, and the power delivery to the MacBook gets unstable. That instability causes the backlight to flicker.

The Fix: Two Steps, Not One

You need to do both of these steps. Doing just one might reduce the flicker, but it won't completely stop it. I've tested this on multiple U2720Q units with MacBook Pro M1 and M2 models.

Step 1: Update the Monitor's Firmware

Dell released a firmware update (version M2B102 or later) that specifically addresses USB-C flickering. Here's how to get it:

On your MacBook, go to Dell's support website. Search for 'U2720Q' and go to the 'Drivers & Downloads' section.
Download the file named Dell U2720Q Monitor Driver and Firmware Update Utility (it's an .exe file, but don't worry—you'll run it on your Mac).
Connect the monitor to your MacBook using the USB-C cable. Make sure the monitor is on and showing your Mac's desktop.
Open the downloaded .exe file. macOS will give you a warning about it being from an unidentified developer. That's normal. Right-click the file and choose 'Open' from the menu, then click 'Open' again in the pop-up.
The utility will run and detect the monitor. It shows the current firmware version and the new one. Click 'Update' and wait.
After the update finishes, the monitor will restart itself. You'll see the screen go black for a few seconds. That's expected.

After this step, the monitor should display a message like 'Firmware updated successfully.' If you don't see that, the update didn't complete. Try again, but this time make sure no other USB devices are plugged into the monitor's USB hub.

Step 2: Change the USB-C Prioritization Setting

Firmware alone didn't fix it for everyone. You also need to change a setting in the monitor's on-screen display (OSD) menu.

Press the joystick button on the back of the monitor (it's the one that looks like a small stick, located on the bottom-right edge when you're facing the screen).
The OSD menu appears. Tilt the joystick up or down to highlight 'System' and press the joystick in to select it.
Now look for 'USB-C Prioritization.' It's usually the second option. It defaults to 'High Resolution.' Press the joystick in to change it.
Select 'High Data Speed' from the list.
Exit the menu. The monitor will renegotiate the connection with your MacBook. The screen might go black for a second, then come back.

That's it. The flicker should be gone. I know it sounds counterintuitive—you'd think 'High Resolution' would be the right setting for a 4K monitor. But the U2720Q already sends a full 4K signal at 60Hz over USB-C. The 'High Resolution' setting actually forces a higher bandwidth mode that the monitor's hardware can't handle reliably with power delivery. 'High Data Speed' keeps the 4K resolution but fixes the power negotiation.

What to Check If It Still Flickers

If you've done both steps and the flicker persists, here's what to look at next:

The cable. I said it's not the cable, but if your cable is damaged or is a third-party one, it can absolutely cause flicker. Use the cable that came in the box. If you lost it, buy a USB-IF certified USB-C cable that supports 5A and 10Gbps. Don't get a cheap one.
Your MacBook's power adapter. If you're running the MacBook on battery, the monitor might still flicker because power delivery is limited. Plug your MacBook into its own power adapter. If the flicker stops, the issue is power draw, not the monitor.
Other USB devices. Unplug everything from the monitor's USB ports. A faulty USB device (like a hub or a phone charging) can cause interference.
macOS settings. Go to System Settings > Displays. Make sure the refresh rate is set to '60Hz' and not 'Variable (40-60Hz).' Variable refresh can cause subtle flickering on some monitors.

If none of that works, you might have a defective unit. Dell's warranty covers this monitor for three years. Contact Dell support and tell them you've done the firmware update and changed the prioritization setting. They'll usually replace it without much hassle.