External monitor not detected on your Mac?

Steps

1. 01

   Check the cables, the adapter and the port

   • Make sure the display's power and video cables are firmly in at both ends, and the display is switched on
   • Use a Thunderbolt, USB-C or HDMI port on the Mac; an adapter must support DisplayPort Alt Mode, Thunderbolt 3 or Thunderbolt 4
   • Using a hub or dock? Connect the display straight to a port on the Mac to test

   Why?

   Similar-looking ports aren't all the same — Apple advises identifying the port before blaming the display.

2. 02

   Check your Mac supports that many displays

   • Apple menu›System Settings, then Help in the menu bar → '[your Mac] Specifications'
   • Scroll to Display Support or Video Support for the maximum number of external displays and resolutions

   Why?

   Limits depend on the Mac, the display, the cable and what else is connected — one display over the limit simply stays dark. For example, MacBook Air with M1 or M2 supports one external display — check your own model's specifications.

3. 03

   Make macOS look again

   • Disconnect the display from the Mac and from power, then reconnect it
   • Put the Mac to sleep and wake it — on a laptop, close the lid for a few seconds and reopen it
   • System Settings›Displays, hold Option to show Detect Displays, and click it
   • Restart the Mac

   ✓You should see: The display listed in Displays settings, where you can arrange it.

4. 04

   Allow the display to connect

   • On a Mac laptop with Apple silicon, click Allow when asked whether to connect the accessory — if you choose Don't Allow, the display stays dark until you reconnect it
   • The rule lives in System Settings → Privacy & Security → Accessories → 'Allow accessories to connect'
   • Lid closed: keep the Mac on power with an external keyboard and mouse, and allow those too
5. 05

   If it's detected but dark or blurry

   • Apple display: press Brightness Up or use the brightness control in Displays; other displays: use the display's own buttons
   • Blurry: choose the display's native resolution in Displays settings
   • Install the latest macOS update, which also carries firmware for Apple displays; other displays get firmware from their maker

   Also see: Keep macOS updated the safe way