Mac cannot recognize external monitors? Don't worry, this article will guide you through the common problems of failure of Mac connecting to a second monitor. Most problems can be solved by simple troubleshooting methods, such as adjusting settings and checking cable connections.

Improve the display effect of Mac screen

Use Vivid software to break through factory restrictions and increase the brightness of Mac display to a new level. It can be downloaded on the Setapp platform.

Can't detect a second monitor by Mac? How to fix it?

Once the dual monitor is connected, the monitor should automatically turn on and display an extended desktop or mirrored image (depending on the settings). New monitors will also be listed in System Settings > Monitors.

If none of the above situations occur, it means there is a problem. Let's troubleshoot common reasons why Macs can't detect monitors.

1. Use the Detection Monitor option in System Settings

Macs may need to manually identify the second monitor for the following reasons:

• macOS cannot automatically detect external monitors due to temporary software failure.
• There is a compatibility issue between the Mac and the monitor.

Workaround: Use the Detection Monitor option. This will make the Mac search for connected monitors and set them up.

Operation steps:

1. Click the Apple icon > System Settings > Monitor.
2. Press and hold the Option key to change the Night Mode button to Detect Monitor.
3. Click "Detection Monitor" to force the connection.

2. Check cable connections and adapters

If the adjustment settings are invalid, you need to check the cable or adapter. Ensuring that all connections are correct usually resolves the issue.

• Check the cables: First, double check that all cables are securely connected to your Mac and monitor. Loose cables may disrupt connections.
• Check the adapter: If you use the adapter, make sure it is compatible with your Mac and monitor. New Mac models such as the 2024 MacBook Pro and Air use Thunderbolt ports. Older models in 2015 and beyond may use USB-C ports. These ports require specific adapters to connect to external monitors, incompatible or poor quality adapters can cause problems.

Troubleshooting cable problems: Unplug the cable from your Mac and monitor and wait for a few seconds before reconnecting. Sometimes this is enough to reset the connection and clear minor failures between devices.

Note: If your Mac does not have these ports, or you are using a docking station, the quality of the adapter is especially important. Cheap, unreliable adapters can often cause disconnection or no connection at all. It is recommended to invest in high-quality adapters, which will save you a lot of time and hassle!

What if the monitor still doesn't recognize? Try replacing the cable or adapter. For example, if you are using HDMI, try DisplayPort or USB-C (if your monitor supports it).

3. Adjust the display settings for improved compatibility

Adjusting the resolution and refresh rate can usually solve the problem if the display has been detected but displays incorrectly.

Operation steps:

1. On your Mac, click on the Apple icon.
2. Select System Settings > Monitor.
3. Select the compatible resolution that best matches the display specifications.

Tip: Adjusting the resolution and refresh rate can match the display output to the display. The monitor may appear dim or turn off because the brightness is too low. Vivid software can be used to increase the display brightness.

4. Check monitor compatibility and number of monitors supported

The Mac model determines the number of external monitors it supports. Check if your Mac model supports multiple external monitors, as old Intel-based Macs and new M1 and M2 models differ in this regard.

• Most M1 Macs, such as the MacBook Air and the 13-inch MacBook Pro, support only one external monitor.
• The M1 Mac mini is an exception, which supports two – one via HDMI and one via USB-C or Thunderbolt.
• Old Intel-based Macs can support multiple monitors.

Apple's technical specifications include all the necessary information, and you can check whether your Mac model supports external monitors.

5. Restart your Mac and update your software

Restarting your Mac and updating your system software is an easy way to fix your Mac's failure to recognize external monitors. Outdated macOS versions can interfere with the hardware, so restarting your Mac is the best solution.

After restarting, try connecting the monitor again. Still not working properly? The next step is to check for software updates, as outdated versions may have errors that cause problems.

6. Try Safe Mode or reset NVRAM/PRAM

Safe Mode disables unnecessary software extensions and clears system cache to keep the Mac safe from conflicting software.

Start the Mac and enter safe mode:

1. Turn off the Mac.
2. Open it and hold down the Shift key immediately.
3. Release Shift key when the login window appears.

Reset NVRAM/PRAM:

1. Turn off the Mac.
2. Open it and hold Option Command PR .
3. Release the button after 20 seconds.

Mac cannot detect second monitor: Resolved

In some cases, the problem can be simple, such as increasing screen brightness. In some environments, a dim display may be too dark to look like it is off.

FAQ

How to force Mac to detect monitors?

Why can't my Mac detect a second monitor?

Why can't my Mac display via HDMI?

Through the above steps, I believe you can solve the problem that your Mac cannot recognize the second monitor.

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