MacBook Pro M1 external screen flickering

[ajschof]

Hello, guys! 👋​

I visited the eye doctor three weeks ago because I work 8-10 hours in front of displays. During the visit, I mentioned that I've been experiencing eye strain due to my eyes getting worse over the past two years from staring at screens. I've been taking daily pills and using eye drops to reduce the strain, but it hasn't improved. The doctor mentioned that he knew someone at Sony who might be able to help. On Monday, that person called me, and he was sympathetic. He offered to help by inviting me to bring all my laptops (I have a 16" M1 Pro and a 16" M2 Max MacBook) so we could figure out the problem.

Excited about the opportunity, I packed everything into my car and drove to the Sony headquarters. I wasn't sure what to expect, so I brought along a variety of equipment, including three Dell monitors (U4320Q, U2722DE, P3223DE) and a Benq EL2870U. I also had 17 different cables of varying lengths and brands (USB-C, USB-C to HDMI, USB-C to DP, HDMI). I didn't include any dongles because I've had bad luck with them in the past, as they couldn't support 60Hz or 4K resolution at more than 30Hz.

When I arrived at Sony, I met Jakob, the display specialist, who turned out to be a very knowledgeable and helpful person. I was amazed that such an expert would take the time to assist me. We brought everything inside and connected all the devices. Jakob ran a display test, and to my surprise, everything appeared perfect with no display faults, except for a few dead pixels we discovered. It was a relief to know that the displays were in good condition.

Next, Jakob tested all the cables, and surprisingly, everything seemed fine. I was confused because I was certain there was an issue with one of the cables. However, two of the cheap cables from Shengzeng failed the test, confirming my suspicions.

Then Jakob suggested we open up the MacBook to investigate further. I was initially hesitant but decided to give him the older M1 Pro model, just in case anything went wrong. He examined the internals and noticed something missing that is typically found in Windows computers and laptops—a small controller or protective shielding. Even Nvidia, AMD, and the integrated graphics card CPUs usually have this feature. Jakob couldn't find any shielding or the expected controller. It's worth mentioning that he had never worked with an Apple Silicon before, but he seemed confident in his element, focusing mainly on the HDMI and USB outputs. We took a short break, and when we returned, Jakob touched the MacBook lid, and I could feel the familiar vibration that many MacBook users experience. He said, "Aha," and I wasn't sure what he meant at the time.

Jakob then grabbed two HDMI cables for testing—one was a cheap, short, and thick cable that I had never tried before, measuring exactly 1 meter in length. The other was a longer, thinner cable from a premium brand that cost around 43 Euros. To my surprise, the 1-meter thick HDMI cable worked perfectly without any issues, which shocked me.

However, the longer, 2-meter HDMI cable with nylon weave insulation started exhibiting ghosting, flickering, and smearing. It was quite strange. Moving on to USB-C cables, the short and thick one worked fine, but the thinner 0.8-meter cable failed. Jakob then measured the outgoing and incoming voltage, finding no issues with the thick cable. However, when he tested the longer cables, he noticed unstable voltage and signal fluctuations, resembling a zigzag

graph rather than a smooth wave. This perplexed him, suggesting that either there was no voltage regulator or the cables were too thin. The microvolts fluctuated and jumped between the steel connectors on the monitor and MacBook housing. All the USB-C to HDMI and DP cables became extremely hot at the monitor connection, reaching temperatures over 45 degrees Celsius due to excessive power transmission. One cheap USB-C to HDMI cable even reached 73 degrees Celsius, posing a serious danger.

We conducted thorough tests, as Jakob was genuinely interested in finding a solution. I was just happy that the dilemma was resolved, and I could work more comfortably without experiencing eye strain.

Jakob couldn't determine if a proper regulator was built into the MacBook or if the shielding was missing. However, on the thin cables, the MacBook consistently raised and lowered the voltage. Although he didn't want to claim that Apple made a mistake, it certainly seemed that way to him. The voltage fluctuations on the MacBook and the steel housing of the monitor were the root cause of the problem.

Apologies for the long story, but I wanted to provide a detailed description of the problem.

Here's the fix for the issue:

1. Avoid cable lengths over 1 meter (the sweet spot is 0.8-1m max).
2. Check if the cables have thick wires. Thicker wires tend to have fewer problems.
3. Cable insulation is crucial. Rubber cables provide the best performance (avoid nylon, neoprene, and other cheap materials).
4. Stick to the traditional HDMI technology and be cautious with HDMI or DP output dongles.
5. If using a USB-C cable, keep it as short as possible (0.8-1m max) with thick insulation.
6. If you experience flickering, protect your display (the controller may sustain damage) or the MacBook could be at risk of voltage-related damage.
7. Avoid steel cases for USB-C and HDMI connectors (plastic or rubber is ideal).

HDMI cables are currently the best option, particularly those with lengths of 0.5m and 1m. Choose cables with a thick, chunky design, appropriate wire thickness, top-notch insulation, and a rubber casing.

!!! HDMI for order or view !!!


For USB-C enthusiasts, go for 0.5m and 1m cables without flickering issues. Look for thick USB-C cables with a rubber casing.

!!! USB C for order or view !!!

*Please note that I've tested all these cables, and they work perfectly. Cheaper cables may also work, but you may experience slight flickering. However, ghosting can be avoided by keeping the cable length under 1 meter and ensuring it has sufficient thickness.*

**I've conducted tests on 17 cables and 4 monitors with an expert, and now I can enjoy Dark Mode, Dark Reader, and the dark Apple backgrounds without any issues.**

P.S. I hope my English was good enough; I learned English a few years ago.
P.P.S. Special thanks to Jakob from Sony DACH! 😗💋💋💋

****EDIT SONOMA BETA VERSION 3.0 ****​

Here is a small EDIT from me, as it was claimed that the problem no longer exists with Sonoma. I have tested all cables again, including USB-C to HDMI and DP. The difficulties with the USB-C to HDMI and DP cables have even worsened, while HDMI and USB-C to C runs smoothly. One just needs to adjust the settings, then restart the Mac and there is no flickering or ghosting. However, ghosting appears to be much more intense on the USB-C to HDMI and DP cables.

Cable Testing and Results:

• USB-C to USB-C (thick cable) works perfectly (50cm and 1 Meter)
• HDMI to HDMI (thick cable) also works perfectly (50cm and 1 Meter)

***Please do not be fooled into thinking that changes have been made. This is not a software-related issue, but it lies in the hardware.***

I spoke with Jakob today, he suggested insulating the contacts with insulating tape to prevent voltage from jumping to the casing. However, one must be extremely careful as the tolerances are very small. I will try this suggestion later this evening.

Do not be led astray. If it was a software error, the screen manufacturers and Apple could find a solution. But since it's a hardware issue, little can be done except to reduce or eliminate the voltage with thick cables.

After I have tried the insulating tape, I will report back. It's a delicate task to isolate the port laterally around the socket and then to isolate the connector.

**** Another important note I would like to make: Whenever you plug in and unplug the cables and make the settings you want, then leave everything as it is and don't change anything. After that, it is important to restart and leave the settings unchanged. As soon as you change anything, a restart must be done! ****​

I'm not an expert in this area but it may be to do with how stray currents/voltage from ungrounded appliances flow through a monitor or the MacBook. Stray voltage is the occurrence of electrical potential between two objects that ideally should not have any voltage difference between them.

I have a pair of Logitech Z207 speakers connected to a power strip that my monitor and MacBook are also connected to. The AUX cable is connected to my monitor's headphone jack. Now I noticed that the plug for the speakers is ungrounded, which should be standard for UK plugs. I've since removed the speakers and the issue seems to happen a lot less. AUX cables are very susceptible to ground loops and noise as they pick up interference relatively easily. It's possible that stray currents are flowing from the speakers through the AUX cable, through the monitor, then through the USB C to USB C cable that provides the video.

I've done some research and found some posts that may or may not back up what I'm suggesting even though they're not entirely related to this problem [1][2].

It is highly unlikely that the display symptoms are coming directly from the MacBook (i.e. the image source). I've found that the image retention persists between input sources, including my Xbox, which eventually fades. What we can't seem to figure out is why a MacBook can cause monitor issues.

Long story short, I think this is an issue where neither the MacBook or the monitor are acting solo to cause this issue but more of a problem on either side. Try checking for anything connected to either your monitor or MacBook that could cause these stray currents/voltages (i.e. with ungrounded plugs) and remove them. Keep devices that are connected to one another (e.g. AUX cable, HDMI cable, USB C cable) on a common grounding point like a power strip (with a grounded plug) but ensuring that you don't overload it (check max amps, usually 13A in the UK), ensuring that every device has a grounded plug. The idea is to minimise the chances of a ground loop forming and to keep the voltage stable.

That's my theory anyway. Please correct me if what I've said isn't right.

 

[ajschof]

Pretty sure it is no hardware issue. Maybe with codecs or something I don't know but when I airplay mirror to my Apple TV 4K I get the flickering too. The TV is not connected to the MacBook (except wifi/ethernet of course)

Could you provide a video of this happening? I don't think this has been reported before. AFAIK it's only been observed to happen over wired.

 

[ajschof]

I'm not an expert in this area but it may be to do with how stray currents/voltage from ungrounded appliances flow through a monitor or the MacBook. Stray voltage is the occurrence of electrical potential between two objects that ideally should not have any voltage difference between them.

I have a pair of Logitech Z207 speakers connected to a power strip that my monitor and MacBook are also connected to. The AUX cable is connected to my monitor's headphone jack. Now I noticed that the plug for the speakers is ungrounded, which should be standard for UK plugs. I've since removed the speakers and the issue seems to happen a lot less. AUX cables are very susceptible to ground loops and noise as they pick up interference relatively easily. It's possible that stray currents are flowing from the speakers through the AUX cable, through the monitor, then through the USB C to USB C cable that provides the video.

I've done some research and found some posts that may or may not back up what I'm suggesting even though they're not entirely related to this problem [1][2].

It is highly unlikely that the display symptoms are coming directly from the MacBook (i.e. the image source). I've found that the image retention persists between input sources, including my Xbox, which eventually fades. What we can't seem to figure out is why a MacBook can cause monitor issues.

Long story short, I think this is an issue where neither the MacBook or the monitor are acting solo to cause this issue but more of a problem on either side. Try checking for anything connected to either your monitor or MacBook that could cause these stray currents/voltages (i.e. with ungrounded plugs) and remove them. Keep devices that are connected to one another (e.g. AUX cable, HDMI cable, USB C cable) on a common grounding point like a power strip (with a grounded plug) but ensuring that you don't overload it (check max amps, usually 13A in the UK), ensuring that every device has a grounded plug. The idea is to minimise the chances of a ground loop forming and to keep the voltage stable.

That's my theory anyway. Please correct me if what I've said isn't right.

Debunked my own theory, it's back. Probably software related as BetterDisplay triggered it straight away and not gradually like it usually appears with 1440p 120hz.

 

[titaniumdoughnu]

Is this the same issue?

I am having a sporadic issue where the monitor (LG DualUp) starts rapidly flickering a ghost image of something I was displaying in the past. The ghost image returns after a power disconnect (up to 10-20 minutes so far), survives restart of the computer, and even appears again when the monitor is plugged back in to power only after a time, and not connected to the computer in any way.

I'm struggling to see how this could be anything to do with the computer, but it does sound like some people up-thread are talking about a similar issue.

Specs: Mac Studio M2 Ultra and LG DualUp display as secondary display. Primary display (which is fine) is an Apple Studio Display.

 

[CalMin]

Is this the same issue?

I am having a sporadic issue where the monitor (LG DualUp) starts rapidly flickering a ghost image of something I was displaying in the past. The ghost image returns after a power disconnect (up to 10-20 minutes so far), survives restart of the computer, and even appears again when the monitor is plugged back in to power only after a time, and not connected to the computer in any way.

I'm struggling to see how this could be anything to do with the computer, but it does sound like some people up-thread are talking about a similar issue.

Specs: Mac Studio M2 Ultra and LG DualUp display as secondary display. Primary display (which is fine) is an Apple Studio Display.

I had this with a Dell. Never could diagnose it. Had to return.

I tried cables and docks, but always the flicker. I think it was some fundamental difference between how Apple does things with Apple silicon and how just about every other computer on the planet works. So frustrating.

It's one of the reasons that I kept the Apple studio display because 'it just works'.

 

[svenmany]

Is this the same issue?

I am having a sporadic issue where the monitor (LG DualUp) starts rapidly flickering a ghost image of something I was displaying in the past. The ghost image returns after a power disconnect (up to 10-20 minutes so far), survives restart of the computer, and even appears again when the monitor is plugged back in to power only after a time, and not connected to the computer in any way.

I'm struggling to see how this could be anything to do with the computer, but it does sound like some people up-thread are talking about a similar issue.

Specs: Mac Studio M2 Ultra and LG DualUp display as secondary display. Primary display (which is fine) is an Apple Studio Display.

Certainly my LG monitor continued to have issue after disconnecting it from the computer and disconnecting/reconnecting power. But, it always seemed to resolve within a couple of minutes and I've never seen the image without the computer being subsequently connected to the computer.

I haven't had any issues in a long time with my LG. I turn off my monitors every night and don't use dark mode. However, now and again my Innocn flickers; turning off and on the monitor fixes it.

 

[titaniumdoughnu]

Certainly my LG monitor continued to have issue after disconnecting it from the computer and disconnecting/reconnecting power. But, it always seemed to resolve within a couple of minutes and I've never seen the image without the computer being subsequently connected to the computer.

I haven't had any issues in a long time with my LG. I turn off my monitors every night and don't use dark mode. However, now and again my Innocn flickers; turning off and on the monitor fixes it.

My issue is so extreme, I feel like everyone in this thread would be describing this if it happened to them.
This has me leaning toward it's a fault with the LG, and *maybe* the Mac bug is what triggered it, but it's way worse than normal.

I let the monitor rest disconnected from power overnight, and 12+ hours later, it is still showing the retained image, connected only to power, no computer connection.

 

[svenmany]

My issue is so extreme, I feel like everyone in this thread would be describing this if it happened to them.
This has me leaning toward it's a fault with the LG, and *maybe* the Mac bug is what triggered it, but it's way worse than normal.

I let the monitor rest disconnected from power overnight, and 12+ hours later, it is still showing the retained image, connected only to power, no computer connection.

I and others suspect that the flickering can damage a monitor. Perhaps this happened to yours.

 

[lenteo]

More datapoints:

I have an M1Max Mac Studio at home (with a BenQ EW2780U, 4K) and an M2 Mac mini in my office (with a BenQ PD2500Q, 2K and a Dell P3421W, 2K):

1. M1Max+EW2780U encountered the flickering quite often. Interestingly, on this monitor, the issue always appears on the top half of the screen, regardless of I placed the monitor vertically or horizontally.
2. M2+P3421W: only once.
3. M1Max/M2+PD2500Q: never.

 

[LostProgrammer]

I have what I believe is wonderful news.

Back on the first of January 2022, I reported the bug to Apple after having issues occur with my Dell S2722QC monitor. I spoke to multiple people at Apple who all tried to work out why the issue was occurring. I contacted Dell support who kindly sent me a second monitor to see if the issue occurs on a different monitor. To great surprise, the issue was present on the second monitor too.

There were many "thought to be" solutions such as:
• Changing refresh rate from 'Variable 40Hz-60Hz' to '60Hz'
• Turning off 'True Tone'
• Changing the Colour Profile on macOS to 'Colour LCD'
• Being on the most recent version of macOS
• Using HDMI rather than DisplayPort over USB-C

To explain the flickering, it is complicated. It's like having the content you were looking at burnt into the display like OLED burn-in. The display also flickers a lot, it's like pulsing really fast. You can try turning the monitor off, I turned mine off for a week and the flickering was still there when turning it back on. This flickering has been an absolutely painful problem to deal with.

Here's a video I captured back in 2022 when reporting it to Dell and Apple:
https://drive.google.com/file/d/1jWwT6Db197uNHjJQfs9Dgy7s2bRn8hjW/view?usp=sharing

Today, after 2 and a bit years, two entire macOS versions later, I receive a response from Apple saying that there are changes to macOS Sonoma 14.4 which may fix this issue.

After countless hours using my monitor with my MacBook Pro 14" M1 Pro through DisplayPort, I can say with some confidence that the issue is not occurring. I am on macOS Sonoma 14.5 (Beta) so it may not be fixed on Sonoma 14.4 as Apple said in their email. I won't be amazed if the issue shows up somewhere else now, maybe some colours in an image on Google somewhere may cause it but we will see.

I have tested to see if it is fixed by going back to my original 13" M1 MacBook Pro from late 2020. This good old laptop is running macOS Sonoma 14.4.1 which is the most recent version of macOS available to the public. During testing, the flickering occurs anytime comments on YouTube are shown or when watching YouTube Shorts. The trigger for the flickering changes all the time. Back when the issue first began, it was an image of a portfolio website on Google, then it was Rivian's website showing their R1T. The trigger has changed so many times over the past 2 years that I have failed to keep track of what has caused it.

With all this said, macOS Sonoma 14.5 may or may not fix the problem you are experiencing but I really hope it is the solution to end the problem for good for everyone. If you still have the issue occur after doing the next update when it is released to public (14.5), use Feedback Assistant on macOS to report the bug with as much detail as you can provide so the problem can be dealt with.

The email from Apple:

There are changes in build macOS Sonoma 14.4 or later that may have resolved this issue. Is this issue fixed for you in this build? If you are still seeing this issue, please provide any reproduction steps so we may investigate further.

 

[drunkmouth]

I think I've found a solution of editing the monitors EDID information using AW EDID Editor to remove the Ycbcr flag and re-uploading it with BetterDisplay. Been a couple of days with no flickering now.

 

[skybox]

Just now using BetterDisplay (current version), I was able to turn the flickering on and off(!) per display by turning "GPU dithering" off under image adjustments for my external displays. I will edit this if anything changes but it seemed to be a switch for this issue, turning it on and off at will which was crazy. It even sounds like the sort of thing that would cause this. Please try this and let me know, hoping this helps others! (I also hope Apple really fixed it as LostProgrammer said.)

 

[Fishrrman]

drunk wrote:
"I think I've found a solution of editing the monitors EDID information using AW EDID Editor to remove the Ycbcr flag and re-uploading it with BetterDisplay. Been a couple of days with no flickering now."

Could you elaborate on this a bit?
Steps taken, in order?

I'm sure a more detailed "how to" would be a BIG help to a lot of folks with the same problems...

 

[drunkmouth]

drunk wrote:
"I think I've found a solution of editing the monitors EDID information using AW EDID Editor to remove the Ycbcr flag and re-uploading it with BetterDisplay. Been a couple of days with no flickering now."

Could you elaborate on this a bit?
Steps taken, in order?

I'm sure a more detailed "how to" would be a BIG help to a lot of folks with the same problems...

Sure, will report back tonight with the steps and screenshots!

 

[aquelemiguel]

Just now using BetterDisplay (current version), I was able to turn the flickering on and off(!) per display by turning "GPU dithering" off under image adjustments for my external displays. I will edit this if anything changes but it seemed to be a switch for this issue, turning it on and off at will which was crazy. It even sounds like the sort of thing that would cause this. Please try this and let me know, hoping this helps others! (I also hope Apple really fixed it as LostProgrammer said.)

View attachment 2367719

This is the way. Unfortunately my Sonoma 14.5 beta build still has the flickering issue, but just like @skybox, I am also able to toggle the flickering on and off with this GPU dithering option.

After months of toggling TrueTone, tweaking refresh rates and messing with colour profiles with no real success, I can finally rest. Great find @skybox, thank you so much.

 

[LostProgrammer]

This is the way. Unfortunately my Sonoma 14.5 beta build still has the flickering issue, but just like @skybox, I am also able to toggle the flickering on and off with this GPU dithering option.

After months of toggling TrueTone, tweaking refresh rates and messing with colour profiles with no real success, I can finally rest. Great find @skybox, thank you so much.

It's rather interesting that the update has not fixed the issue for you. I will be sure to let Apple know, would you be able to provide me with the model of MacBook you are using, the display model you are experiencing the issues with and the connectivity method you are using? e.g.
Device: MacBook Pro 14" M1 Pro (A2442)
Monitor: Dell S2722QC
Connection: DisplayPort

 

[Yassin95]

Just now using BetterDisplay (current version), I was able to turn the flickering on and off(!) per display by turning "GPU dithering" off under image adjustments for my external displays. I will edit this if anything changes but it seemed to be a switch for this issue, turning it on and off at will which was crazy. It even sounds like the sort of thing that would cause this. Please try this and let me know, hoping this helps others! (I also hope Apple really fixed it as LostProgrammer said.)

View attachment 2367719

Thank you so much!!!! i created this just to thank you @skybox !!