External monitor flicker on Macs, particularly those with M1, M2, and M3 chips, is a frustratingly common issue. While the precise cause can be elusive, ranging from software glitches to hardware incompatibilities, this comprehensive guide provides a step-by-step approach to troubleshooting and resolving this problem. We’ll delve into the latest macOS updates addressing the issue, examine compatibility problems with specific monitor models, and explore solutions gleaned from Reddit and Apple Support Communities. This guide will offer the most effective strategies for a flicker-free experience.

Troubleshooting for Flickering External Monitors

Before diving into advanced troubleshooting, let's start with the basics. Many users find that these simple steps resolve the flickering issue:

1. Restart Your Mac and Check for Updates: A simple restart often resolves minor software glitches. After restarting, immediately check for macOS updates via System Preferences > Software Update. The December 2023 macOS 15.1 update specifically addressed external monitor flicker reported by M1/M2/M3 chip users experiencing horizontal line flickering and signal loss. Remember, even if you believe your macOS is current, a recent update may not be immediately applied to your system.

   

2. Connect Using a Different Port or Cable: Try connecting your external monitor using a different USB-C port on your Mac. If using a dongle or dock, try connecting directly to a Thunderbolt 3 or USB4 port for optimal performance. Faulty cables are a frequent culprit; test with a known-good cable. Several users reported success switching from HDMI to DisplayPort, or USB-C to HDMI adapters. The data suggests that cable quality and type significantly impact stability.

   

3. Disable Variable Refresh Rate (VRR) and Adaptive Sync: Features like Adaptive Sync (FreeSync/G-Sync) dynamically adjust the refresh rate to match the content frame rate. While beneficial for smooth video playback, this can sometimes cause flickering. This is especially pertinent to monitors like the LG Ultragear 1440p 165Hz where Adaptive Sync issues have been linked to motion-based flickering. To disable these features, navigate to your monitor's on-screen display (OSD) menu. If your monitor's OSD menu does not offer this option, navigate to System Preferences > Displays and adjust the refresh rate to a fixed value.

   

4. Check Your Dongles and Monitor Settings: If using a USB-C hub or dongle, make sure it's properly powered and compatible with your monitor and Mac. Check your monitor's settings for features such as Black Frame Insertion (BFI) or "blur reduction," which can sometimes cause flicker. Some monitors have settings for Dynamic Contrast Adjustment or Brightness-enhancing technology that also can be responsible for the flickering. Try switching those off. If you're using HDR mode, switch that off as well.

   

5. Consider "StillColor" and Temporal Dithering: A third-party utility called StillColor can help resolve image noise/artifacts. Some users suggested that turning off temporal dithering can contribute positively to reducing screen artifacts. However, proceed with caution. Sometimes manual manipulation of such graphical elements can lead to unpredictable side effects, especially if the user doesn't completely understand the concepts involved.

Troubleshooting for Dual Monitor Flicker on Mac

If you're using two external monitors and experiencing flicker on one or both, the troubleshooting steps are similar to those for a single monitor. However, some additional considerations apply:

• Connection Type: Ensure both monitors are connected using compatible ports and cables (Thunderbolt 3/USB4 preferred).
• Daisy Chaining: Avoid daisy chaining monitors (connecting one monitor to another). Connect each directly to the Mac for best results.
• Display Settings: Check System Preferences > Displays for correct resolution and refresh rate settings for both monitors.

Remember to test each monitor independently to isolate the problematic display.

Common Causes of External Monitor Flicker on Mac

Numerous factors can contribute to external monitor flicker. While not an exhaustive list, these are among the most frequent causes:

• Compatibility Issues with External Monitors: M1, M2, and M3 Macs have reported compatibility differences with certain monitor brands and models. For example, issues have been seen with LG, BenQ, and Dell monitors. Specific model issues are well-documented in user reports.

• Problems with USB-C or DisplayPort Connections: The type of connection (USB-C, Thunderbolt 3, DisplayPort, HDMI) is crucial. Direct DisplayPort connections frequently resolve issues when they occur with adaptors. Specific issues observed with USB-C to DisplayPort connections with Dell S2721QS monitors highlights the need for careful selection and testing of cable types and connections.

• Issues with Built-in Display Refresh Rates: Flickering on the external monitor can sometimes be linked to inconsistencies with the internal Mac display's refresh rate. Ensuring both displays operate at compatible refresh rates can effectively reduce inconsistencies.

How to Fix External Monitor Flicker on macOS Ventura 13？

Users on macOS Ventura 13 experienced significant challenges. One user reported intermittent flickering on an LG 27UL850-W monitor connected to a 14-inch MacBook Pro using a USB-C cable. The issue occurred across various video sources (YouTube, Apple TV, Discord), and even the built-in display flickered during video playback.  Despite filing a support ticket, the user received no response from Apple. This highlights the inconsistency in Apple's support response and the significant prevalence of this problem amongst its users.

Following the general troubleshooting steps above is advised, in addition to these Ventura 13-specific recommendations:

• Check Apple's System Status Page: Ensure there aren't any known server-side issues affecting your display.
• Delete Broken Update Files: In the Downloads folder remove any residual installation files that are incomplete or corrupt.
• Examine Graphic Settings: Disable Adaptive Sync if available through your monitor's OSD menu, or set a static refresh rate, and disable BFI within the monitor settings.

Community solutions for Ventura 13 users included switching from HDMI to DisplayPort, as noted by a user with an HP 27-inch monitor, and troubleshooting specific video playback issues on Acer VG272U models.

Compatibility Issues Between Mac Chips and External Monitors

Compatibility is a significant factor. The M1, M2, and M3 chips have limitations on the number of external displays they can support natively. The M1 and M2 chips are generally limited to a maximum of one external display (via Thunderbolt 3/USB4). The M3 chip support is greater, reaching up to three external displays with some workarounds but still presenting challenges. Specific issues include HDMI signal switching to a limited range (YUV Limited Range on some M1 Macs), inconsistent color profiles, and reduced resolution when rotating the display. These issues vary by both macOS version and the exact monitor model. Different Macs also experience different numbers of supported displays; for example, the M3 MacBook Air can support up to three external displays, whereas the M3 Max MacBook Pro can support four, (always with potential workarounds, as some features might require additional software or hardware).

Using DisplayLink docks can sometimes extend the display capabilities, but it does introduce minor latency, potentially impacting performance-sensitive tasks. This is particularly important to consider as the user needs to balance performance considerations with the desire for an improved user experience.

Furthermore, compatibility problems exist with specific monitor brands. Eizo ColorEdge models, for instance may require changing the monitor's signal format to 'PC' to avoid YUV limited range signal issues. BenQ monitors sometimes only support 4K resolution at 30Hz. Dell monitors, although seemingly broadly compatible, report flickering on USB-C to DisplayPort connections. Information on LG monitor compatibility is sparse, while older NEC monitors were previously reported to show no image on M1 Macs—a problem solved by a firmware update.

Reddit Solutions for Mac External Monitor Flicker (MacBook Pro)

Reddit and community forums offer a treasure trove of user-reported fixes. For M3 MacBook Pros, recent reports include flickering and strobing effects in Firefox (resolved by switching USB-C ports), and the appearance of vertical grey lines on an external monitor (partially resolved by changing display profiles). Common user tips include:

• Using USB-C for Connection: The use of USB-C connections tends to report better stability for external monitors, but this isn't always guaranteed.
• Trying Different Cables: Faulty cables are a common problem, and it's essential to always use high quality cables and connectors.
• Adjusting Display Settings: Experimenting with different refresh rates and resolutions (through System Preferences > Displays) can resolve the issue.
• Updating Drivers: Ensure your macOS and monitor firmware are updated to the latest versions.
• Varying Browser Choice: if the flickering is browser-specific, change to a different browser for testing.

Apple Support on External Monitor Flicker

Apple Support Communities and MacRumors Forums reflect the persistence of the external monitor flickering issue. Recent discussions emphasize faulty or incompatible cables, display settings misconfigurations, and potential macOS compatibility issues as common causes. In addition to general troubleshooting steps, these forums suggest:

• Changing Refresh Rate: Selecting a fixed refresh rate (e.g. 60Hz) often resolves flickering issues.
• Resetting SMC and NVRAM: This can address various system-level problems that may be contributing to the issue.
• Switching Between Different Ports and Connections: switching between Thunderbold ports can help.

User experiences range from simple fixes (changing cables or adjusting display settings) to persistent problems requiring more involved troubleshooting, and a lack of response in some cases from Apple technical support. 

Conclusion

External monitor flickering on Macs is a complex yet solvable issue. By following the systematic approach outlined in this guide, understanding the common causes, and leveraging the collective wisdom of online communities and support forums, you can significantly increase your chances of achieving a flicker-free experience. Remember, careful attention to cable quality, compatibility, and display settings is paramount. While Apple's support may not always be readily available, persistence and documentation of the issue are crucial for effective management and resolution. The combination of direct steps and user-provided insight, leveraged with the data provided in this article, provides a powerful approach to addressing this common issue.

We hope this comprehensive guide has given you some insights into how to fix mac external monitor flicker with M1, M2, and M3 chips. If you have any further questions or would like to share your experiences with these innovative devices, please leave a comment below. Don't forget to share this article with your friends and colleagues who may benefit from the information. Happy browsing! 

FAQs

My M1 MacBook Air flickers with an LG UltraFine 4K display. What else should I try?

Try disabling features such as Adaptive Sync, VRR, BFI, or dynamic contrast in the monitor’s OSD menu. In macOS Display Settings, test different resolutions and fixed refresh rates. Also check for monitor firmware updates, reset SMC/NVRAM, and ensure macOS is fully updated. If issues persist, contacting Apple Support may be necessary.

Why does my external monitor flicker only during video playback on Mac?

Video playback increases bandwidth and refresh demands. Flickering may be caused by hardware acceleration, browser-specific issues, or cable bandwidth limits. Try lowering video resolution, disabling hardware acceleration, switching video players or browsers, and using high-quality cables.

One of my dual monitors flickers on an M3 MacBook Pro. How should I diagnose it?

Start by disconnecting one monitor to isolate the issue. Test different cables and ports, check refresh rate mismatches between monitors, and ensure both displays use compatible resolution and refresh settings. Update macOS and monitor firmware, and reset SMC/NVRAM if needed.