Connecting my Macbook Pro to iMac display

[Pbwj]

I'm trying to use my old iMac as a 2nd display with my new 16" mbp. Can someone tell me which cable/adapter I need to achieve this? I would like to have it display 5k if possible.

iMac Retina 5K, 27-inch, Late 2014 is the model. I have a thunderbolt 2 to thunderbolt 2 cable, Apple looks like they sell thunderbolt 3 to thunderbolt 2 adapter for $50. Would this display in 5k?

 

[chscag]

I don't believe your iMac Retina 5K supports Target Display mode but it should work with the Thunderbolt 3 to Thunderbolt 2 adapter. You might want to check Amazon to see if you can get that adapter for less.

 

[theluggage]

I'm trying to use my old iMac as a 2nd display with my new 16" mbp.

Sorry, but no 5k iMac supports Target Display Mode at all - end of.

iMac (Retina 5K, 27-inch, Late 2014) and later iMac models can't be used as Target Display Mode displays.
https://support.apple.com/en-us/HT204592

Your alternatives include:

- Mac OS built-in screen sharing (lots of restriction - not really a second display solution)
- Luna Display (https://lunadisplay.com/) - I can't vouch for that personally

...both of which send the screen image over a network or wifi connection, so expect lag and artefacts.

The other slightly off-piste suggestion is to use Synergy (https://symless.com/synergy) - it doesn't share the display, but it does let you seamlessly operate two computers from a single mouse/trackpad/keyboard simply by 'mousing' between screens - including some measure of cut'n'paste support. If you combine it with file sharing, it's perfect for (say) viewing reference material on one machine while working on the other.