A second monitor that stays dark on a MacBook Air is often the design limit, not a fault, and the limit changes by generation. Apple's tech specs list the M2 Air with one external display up to 6K at 60Hz; the M3 Air with one external display plus a second up to 5K at 60Hz when the lid is closed; and the M4 Air with up to two external displays at up to 6K at 60Hz. Apple's external-display article adds the cable side: the video cable and any adapter must support the display's resolution and refresh rate, and a USB-C or Thunderbolt adapter must comply with DisplayPort Alt Mode, Thunderbolt 3 or Thunderbolt 4. Connect the display straight to the Air, not through a hub, to test.
Differential
Likely causes of “Apple MacBook Air external monitor is not detected or uses the wrong resolution”, and how to tell them apart
- 1
Too many displays for the model
What separates it A second monitor stays dark on an M2 Air
How to confirm Apple's tech specs list one external display on the M2, one plus a lid-closed second on the M3, and two on the M4
- 2
A cable or adapter that cannot carry the signal
What separates it The display is dark or stuck at a low resolution or refresh rate
How to confirm Apple says the cable and adapter must support the display's resolution and refresh rate and comply with DisplayPort Alt Mode, Thunderbolt 3 or Thunderbolt 4
- 3
A hub or dock in the way
What separates it The display works when connected to a Mac port directly
How to confirm Apple says to connect the display to a port directly on the Mac, not through a hub
- 4
Closed-lid mode without power or input devices
What separates it The lid is shut and the display stays dark
How to confirm Apple says the Mac must be connected to power and using an external keyboard and mouse
- 5
The Mac has not detected the display
What separates it The display is powered and cabled but does not appear in Displays settings
How to confirm Hold Option in Displays settings to show Detect Displays, or sleep and wake the Mac
Before you touch a setting
Record this first — changing settings destroys the evidence
- Which MacBook Air you have (M2, M3 or M4, 13 or 15 inch)
- The monitors, their resolutions and refresh rates and how many you are connecting
- The cable, adapter, hub or dock in the chain
- Whether the lid is open or closed and what System Settings, Displays shows
Try in this order
0 of 7 completedCount the displays
ReversibleCompare the number of displays with the limit for your Air: one on the M2, one plus a lid-closed second on the M3, two on the M4.
Go direct
ReversibleConnect the display to a USB-C port on the Air with a certified cable and no hub.
Check cable and adapter
ReversibleUse a cable rated for the display's resolution and refresh rate; adapters must support DisplayPort Alt Mode or Thunderbolt.
Detect displays
ReversibleSystem Settings, Displays, hold Option and click Detect Displays. Or sleep and wake the Mac.
Lower the resolution
ReversibleIf the display is stuck on a low mode, choose a resolution and refresh rate the cable supports.
Check closed-lid rules
ReversibleFor lid-closed use, connect power and an external keyboard and mouse first, then wake the Mac from the external keyboard.
Restart
ReversibleRestart, by restarting the Air with the display attached, and then testing the display again.
Model-specific
What is true of this model and not of its siblings
- Display limits by model
- M2: one external display up to 6K at 60Hz. M3: one up to 6K at 60Hz plus a second up to 5K at 60Hz with the lid closed. M4: up to two external displays up to 6K at 60Hz. Per Apple's tech specs.
- Ports
- Two USB-C ports (Thunderbolt 3 on M2 and M3, Thunderbolt 4 on M4) and MagSafe 3. No HDMI port.
- Part numbers
- No part number is involved. Adapters and cables are third-party accessories chosen by resolution, not by an Apple part number.
- Repair cost
- A display or port repair is quoted by Apple after diagnosis. iFixit's table lists Apple's US estimate for a MacBook Air battery at $159, the only published fee.
- Other models this page answers
- These steps also fit the MacBook Air 15-inch (M3), MacBook Air 15-inch (M4).
Stop boundary
When this stops being a self-service repair
- !If a single display on a direct cable is dark after Detect Displays and a restart, try another cable and port before booking service
- !If the Mac itself will not detect any display on either port, contact Apple
- !If a hub or dock is the only failing part, contact the maker of the hub
Evidence ledger
Sources behind this answer
Cables, adapters, closed-lid use, hubs, per-model display limits and detecting displays.
Ports, MagSafe 3, Wi-Fi 6, one external display, four speakers, adapters and weight.
Wi-Fi 6E, one external display plus a second with the lid closed, adapters and weight.
Six-speaker system, 3.3 lb weight and the same ports and display limits as the 13-inch M3.
Thunderbolt 4, two external displays, 12MP Center Stage camera, adapters and weight.
The 15-inch M4 with six speakers and the same ports and display limits.
Fanless design, one and two external display limits by generation, SSD, memory and the M5 generation.
Exact questions
Common questions
How many external displays does each Air support?+
Apple's specs: M2, one external display up to 6K at 60Hz. M3, one up to 6K at 60Hz plus a second up to 5K at 60Hz with the lid closed. M4, up to two at up to 6K at 60Hz.
Why is my second monitor dark on an M2 Air?+
Apple lists one external display for the M2 Air. A DisplayLink dock is a workaround for extra screens, but Apple's own specs list one.
What does closed-lid mode need?+
Apple says the Mac must be connected to power and using an external keyboard and mouse, and the display must be connected to the Mac.
Can I use HDMI?+
The Air has no HDMI port. Apple's M2 specs list VGA, HDMI and DVI output through adapters sold separately, and the adapter must meet the display's needs.
Why is the picture blurry or only 30Hz?+
Apple says the cable or adapter may not support the resolution and refresh rate. Use a cable rated for the display and connect it directly to the Mac.
How do I detect a display?+
In System Settings, Displays, hold Option and click Detect Displays, or put the Mac to sleep and wake it, as Apple describes.
Is Thunderbolt 3 or 4 required for the cable?+
Apple says any USB-C or Thunderbolt adapter must comply with DisplayPort Alt Mode, Thunderbolt 3 or Thunderbolt 4.
Does the 15-inch differ from the 13-inch on displays?+
No. Apple lists the same display limits for the 13-inch and 15-inch of each generation.
external display: model differences
Also covered: Apple MacBook Air 13-inch (2018 to 2020).