imac 21.5 late 2009 as monitor

[Christopher7]

Hi guys, I just got myself a macbook pro 2017.
I wonder if the imac 21.5 can be used as an external monitor for my macbook pro
I've actually read some saying only 27 inch is the only available option but i would like to get some confirmation here

 

[Guy Clark]

You would need to use Target Display Mode. Unfortunately this feature was not introduced to the 21.5" iMac until the mid 2011 release.

 

[294307]

Check this article to see which iMac models support Target Display Mode: https://support.apple.com/HT204592#requirements

Any new iMac from Late 2014 onwards no longer supports Target Display Mode. This was originally due to bandwidth constraints of driving a 5K display. No other Apple computer except for the Mac Pro would have been able to do it at the time.