Use external monitor on MacBook Pro 15" 2017 touch with broken screen ?

Command + F1 will mirror the display (may need to press the "Fn" key to get access to the F1 key). However, this only seems to work once a user is logged into their account. You can log into a user account blind by typing the first character of a user account name (assuming user accounts are normally displayed on the screen) and pressing the "Return" key. Then enter the account password. Give it a minute and you should be able to mirror the display.

Apple has made it extremely difficult to access an external display when the systems still sees the the built-in display as working. You may need to force the laptop into Clamshell mode by closing the lid of the built-in display. You will need to use an external keyboard and mouse. You may need to perform an SMC reset (need to use builit-in keyboard for the SMC reset) and PRAM reset (hold the PRAM reset for a full minute).

Once you get access to the external display you may be able to configure the external display to be the primary display.

sjogren wrote:

Super.

I will try the way with the USB-C adapter because i can't get into the user account blindly on the mac. I don't know the password.

So the next best thing will be trying the way with the ethernet cable directly and Recovery mode or Internet Recovery mode ?

We will see if it lets me do anything that way.

If i have any change with this way. What would i have to do with toggling the mirror mode ?

It won't let you do anything if Filevault is enabled as it would require an admin account password.

If Filevault is not enabled, then you may be able to change a macOS setting to make the external display the primary display, but I have no idea how to do this with macOS. In theory it should be possible, but it may be very difficult to locate this information. I was just trying to provide you some other possible options.

Another option if Filevault is not enabled is to put this laptop into Target Disk Mode and connect it to another Mac (using Thunderbolt or USB) which may allow easier access using a GUI interface than Recovery Mode would offer you which would require the use of the Terminal app and command line. If Filevault is enabled, then you would need an admin password for one of the user accounts.

Having the user log into their account for you is the best option to working around the problem until the laptop can be serviced.

It used to be possible to toggle display mirroring at the login screen before actually logging into a user account. I have no idea why Apple removed this ability. Apple also removed the ability to adjust screen brightness before logging in as well. Makes no sense to me either.

The best chance you have is to log into the laptop blindly so you can mirror the display and possibly configure the external display as the main display.

You could boot into Recovery Mode or Internet Recovery Mode if the laptop is connected directly to the router using an Ethernet cable and a USB-C to Ethernet Adapter which wouldn't require an internal display. Maybe you would be able to toggle mirroring in Recovery Mode or somehow find a way to make an external display the primary display.

I have a friends Macbook Pro 15" touchbar 2017 with broken screen.

The thing is, i tried to hook op an external monitor but still nothing ?

broken screen like cracked glass (?) or

If the GPU itself failed it is a hopeless exercise.

In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test /assessment

Make an appointment for a "hardware issue"—

https://www.apple.com/retail/geniusbar/

Outside the USA

https://locate.apple.com/country

From iOS device using the app to make a online Genius Bar appointment is easy:

https://itunes.apple.com/us/app/apple-support/id1130498044?mt=8

(please note: some delays to be expected with the temporary closure of Apple Stores)

Call (800) MY–APPLE (800–692–7753)

or on line https://getsupport.apple.com/

or call AppleCare Support at 1-800-APLCARE.

Plug the cable into the Mac LAST, once everything on the cable is ready-to-go.

command-F2 will toggle the setting of [√] Mirror displays

power up everything, and have it all ready-to operate.

As the last step, plug in the last cable that plugs directly into the Mac. This often cause the Mac to initiate the "discovery" process, which send a query to the display, asking its name and capabilities. [An external display will not become active unless the Mac sends it a query, and it answers with its name and capabilities.]

Try Command-F1 and command-F2

If no joy, do a Restart of the Mac with the display connected and powered up, ready-to-operate, and see if the display lights up and works. If it shows the desktop wallpaper, it is working as designed.

Like I said Apple has made it extremely difficult to use an external display if the built-in display is still seen by the system. I can confirm the methods I outlined earlier can sometimes work with a 2017 laptop, but even so it can be difficult to achieve. Sometimes I must try it multiple times over and over until it just happens to work. Logging into a user account is probably the best way to achieve it so you can try mirror the display using Command + F1 (or Fn + Command + F1).

This assumes the computer is actually booted to the login screen.

It is doubtful you can use an external display before macOS actually boots.