Q: mid-2010 iMac target display mode alternative

Since your iMac won't support TDM you're limited to a software solution. Screen Recycler will work but it may or may not meet your expectations https://www.screenrecycler.com/ScreenRecycler.html

Sorry no. You're probably out of luck until when/if Screen Recycler is updated and even then you probably would find that it doesn't live up to expectations.

You could try an application called LonelyScreen.

Any updates on this ? Same issue , late 2009 21.5" iMac , can't believe there is no way to use it as a monitor

Use your iMac as a display with Target Display Mode - Apple Support

Your only option is some form of network connection.  Depending on what you are

doing, this may be sufficient.  Best results will be with a gigabit Ethernet connection.

A WiFi connection will work but won't be all that great.  You can try using OSX's built in

Screen Sharing (OS X El Capitan: Screen sharing overview).  There are other solutions

such as VPNs and also Apple Remote Desktop.

woodmeister50, The solutions you are proposing will allow the OP to see the iMac's screen on his Mac but will not allow the OP to extend the OP's Mac's screen onto the iMac.

I Em trying to extend, not mirror.

It doesn't matter. Neither are possible via the options listed by woodmeister50.

Thats what I'm getting at...

Any work around Target Display Mode for

all of the other imac models that do not support it?

to extend the display of a MacBook Pro or another Imac via

mmini display port to mini display port or any software

aalternative ?

For the record Screenrecycler does not support OS 11.XXXX

As I mentioned in an earlier post in this thread, you may want to take a look at LonelyScreen.

Tried it out , works well but this doesnt extend my main monitor, it just mirrors :/