MacBook Air M1: External display only streams 1080p instead of 4K

Hello cafaxo,

Welcome to Apple Support Communities!

If we understand your post correctly, when you have no external display plugged into your MacBook Air M1, and using the Apple TV app, the video plays just fine but once you connect an external display it downgrades the resolution to 1080p. We're here to help!

Let's follow the steps below:

Find out how many displays you can connect

You can connect one or more external displays depending on your Mac model. To find out how many external displays your Mac supports, check its technical specifications page: 

Choose Apple menu  > About This Mac, double-click your serial number, then press Command-C to copy it.

Go to the Tech Specs page, click the Search Tech Specs bar, press Command-V to enter your computer's serial number, then click Search.

Click the specs page for your Mac. The number of displays your Mac supports appears under Video Support or Graphics.

Mac computers with Apple silicon

On Mac computers with Apple silicon, you can connect up to 5 displays depending on the chip in your Mac. To find out which chip your Mac has, choose Apple menu  > About This Mac. 

If you're using a Mac Studio with M1 Ultra:

You can connect up to five external displays to your Mac using the Thunderbolt 4 (USB-C) and HDMI ports on the front and back of the computer.

If you're using a Mac with M1 Max:

On MacBook Pro, you can connect up to four external displays to your Mac using the Thunderbolt 4 (USB-C) and HDMI ports.

On Mac Studio, you can connect up to five external displays to your Mac using the Thunderbolt 4 (USB-C) and HDMI ports on the back of the computer.

If you're using a Mac with M1 Pro:

You can connect up to two external displays to your Mac using the Thunderbolt 4 (USB-C) and HDMI ports.

If you're using a Mac with the M1 or M2 chip:

On MacBook Air, 13-inch MacBook Pro, iMac, and Mac mini, you can connect one external display using either of the Thunderbolt / USB 4 ports. On iMac, connect your display to either of the ports with the Thunderbolt symbol .

On Mac mini, you can connect a second display to the HDMI port.

Using docks or daisy-chaining devices doesn't increase the number of displays you can connect.

Connect your display

Connect your display to power, then connect your display to your Mac. Check the ports on your Mac to find out whether you need an adapter. If you're using a USB-C or Thunderbolt adapter to connect your display, the adapter must be compliant with DisplayPort Alt Mode, Thunderbolt 3, or Thunderbolt 4.

If you use an external keyboard and mouse with your Mac notebook, you can close the built-in display after you connect your external display. You might have to press a key or click your mouse to wake the external display. To use your Mac with the display closed, you need to connect your power adapter or connect an external display that also charges your Mac, such as the Apple Studio Display or 23.7-inch LG UltraFine 4K Display.

If your external display doesn't turn on after you connect it to your Mac, connect your display while your Mac is off, then wake or turn on your Mac.

Use AirPlay

If you have an Apple TV or an AirPlay 2–enabled smart TV, you can use your TV as a separate display for your Mac. Learn how to use AirPlay to mirror or extend your Mac display.

Learn more

Learn what to do if your external display isn't detected or appears blurry when connected to your Mac.

Connect a display to your Mac

Let us know if you have any questions.

Thank you for using Apple Support Communities.

Take care!

Hi cafaxo,

Thanks for letting us know.

Have you tried changing the video resolution for your content? If not, try the steps in the link below in the section titled “Adjust settings for iTunes movies and TV shows.”

Change iTunes movie and TV show settings on Apple TV - Apple Support

Open Settings  on Apple TV.

Go to Apps > iTunes Movies and TV Shows and do any of the following:

Change the video resolution for purchases and rentals: By default, you rent, purchase, and play back iTunes videos in the highest resolution possible, which requires a fast internet connection. If you have a slower connection, select Video Resolution and choose Good.

Turn Quick Start on or off: Select Quick Start to begin playing videos instantly in the best resolution available. You can turn this off if your internet connection is slower.

Note: If Quick Start is turned off, 4K streaming and Dolby Atmos are disabled.

Watch iTunes Movies and TV Shows in standard definition: Select Limit Purchases and Rentals to SD. If you have a slow internet connection, or want to use less data, turn this setting on.

Set wish list sorting order: Select Sort Movies in Wish List, then select either By Date or Alphabetically.

Set favorites sorting order: Select Sort TV Shows in Favorites, then select either By Date or Alphabetically.

We recommend the above steps because they could help address the issue you’re experiencing watching content on your external display.

If the original problem persists after trying the previous steps, please provide us with specifics on what you see for more help, and we will continue from there.

Thanks for using the Apple Support Communities.

Cheers!

cafaxo,

Thanks for verifying that information for us. To help review this further, we recommend to contact Apple Support through this link here: Get Support

Kind regards.