Does the 21.5" iMac support TDM or not?

I have a late 2009 iMac 21.5", you can use it as a display on any Mac that has a Thunderbolt or MiniDisplay (dedicated older port), its the cable or adapter that would make the connection. I use the Mini DisplayPort to Mini DisplayPort cable to make the connection. (Apple no longer carries) but you can grab you one from Amazon, I have a Belkin cable that I got when I first got that iMac. The newer Macs that have the Thunderbolt port on it, would use a the same cable except you plug it into the Thunderbolt port which is backward compatible with Mini Display Port. Per Use your iMac as a display with Target Display Mode - Apple Support the only exception is the iMac (Retina 5K, 27-inch, Late 2014) and later iMac models can't be used as Target Display Mode displays. So the store would have been correct on the 2015 21.5" models. Grab a refurb if that's your ultimate goal from the Apple Online Store.

Hi I managed to use my iMac 21.5in, late 2012 as external monitor. The "command F2" did not work. What worked was opening Finder and selecting my source computer (in this case, a Mac Mini). There you will find the option of sharing the screen.

Welcome to Apple Support Communities

Thunderbolt 21'5-inch iMacs support Target Display mode, but Late 2009 and Mid 2010 21'5-inch iMacs don't support Thunderbolt. See > http://support.apple.com/kb/PH11302

To use the 21'5-inch iMac as an external display, simply connect it with a Thunderbolt cable to another Mac with Thunderbolt, and press Command and F2 keys on your iMac to enable Target Display

You may have already read Use your iMac as a display with Target Display Mode - Apple Support, Apple is VERY clear which iMacs support TDM. Unfortunately no 21.5" iMac from any year (so far) supports it.

Hi, I managed to use iMac (21.5in, late 2012 model) as second screen: go to Finder and you will see an option to share the screen. Now I am using my old iMac as a monitor to my Mac Mini

hi

Ive got two mid 2010 iMacs 21.5" is it possible to connect these together for dual display

The article mentions the iMac with Thunderbolt, and then it mentions the 27-inch iMac with Mini DisplayPort, which are the Late 2009 and Mid 2010 computers. As I told you, Mid 2011 and Late 2012 21'5-inch iMacs have Thunderbolt, so they support Thunderbolt. Have a look at this forum.

leona0123 wrote:

I was told that if I connected the two computers, that I would only be able to transfer data between them, and the displays would not be connected in any way.

You can connect a Thunderbolt Mac to the Thunderbolt iMac for both things, but you need to follow additional steps:

• To enable Target Display mode: press Command and F2 keys on the iMac.
• To enable Target Disk mode (transfer files between Macs without Migration Assistant): hold the T key while your iMac or the other computer is starting

Just throwing my input in. My 2011 21.5" iMac, which is running OS X 10.6.8, supports target display mode just fine via thunderbolt cable. I too was confused after being told both that it did and didn't, but it works.

tammylig wrote:

... So the store would have been correct on the 2015 21.5" models. Grab a refurb if that's your ultimate goal from the Apple Online Store.

You may have missed the fact that this thread is over 2 years old.

hi. i know this thread is old but i have just seen you replied recently, so i was hoping you could help.

i also have a late 2009 21.5 inch imac which i´d like to use as target display for a new macbook pro, and i got a Mini Display Port to Mini Display Port cable to connect the two, but when i press F2 on the imac nothing happens.. can you tell me what you did to make it work? i read everywhere that its only possible with the 27 inch late 2009 imacs, but you seem to have done it with the 21.5 inch.. thanks

I just bought one and its not working either.. I bought the port after reading Apple's site and saw "2009 iMac works" and thought it would work - but then I went back and saw it only says for the 27 inch - I'm guessing it might be due to it having a better processor? Perhaps it worked for the other 2009 person because theirs was upgraded? I wish I knew how to get it to work

Thanks. That was helpful. The table in the link does not specify the size for iMacs 2011. Does that mean TDM is supported in screen sizes other than 27", provided the right cable (thunderbolt) is used?

You need to read and comprehend better, misinformation is not helpful.

You are correct, the information IS very clear which iMacs support TDM, that includes ALL Mid 2011, 2012 and 2014 ( with the exception of Retina models), the 21.5" non-Retinas from 2011 onwards DO support TDM; if you cared to read this thread you'd have read that Star Eater has used their 2011 21.5" in TDM successfully.

There is a lot of arrogance in the Apple community, but it is much much worse when the arrogance is based on ignorance.