I don't think so at least as of mid-2017, I just searched and found videos on how to do the upgrade. Basically turn the thing over, open a latch, and swap out the ram.

The 21 inch model seems to have RAM slots, but not easily accessible like its larger sibling. The 27 inch has 4 user accessible SO-DIMM slots.

iMacs still have a latch to swap out RAM [1]. That, too, may soon be gone. Because on the iMac "Pro"s you have to disassemble the whole unit to get to RAM [2].

[1] https://www.ifixit.com/Guide/iMac+Intel+27-Inch+Retina+5K+Di...

[2] https://www.ifixit.com/Teardown/iMac+Pro+Teardown/101807 and https://everymac.com/systems/apple/imac-pro/imac-pro-faq/ima...

It's been user-replaceable on all but a very few models. Apple even puts a little panel on the 27" models that you can easily pop out to replace on your own OWC has been selling iMac upgrades for a long time, but you can use any brand memory.

In most models there's a door on the back for a quick swap.

https://support.apple.com/en-us/HT201191#install1

In 2017 generation it was not soldered. It's soldered in 21" from 2014 and 2015 years. I think that even CPU is not soldered in latest generation.

thanks all for the answers.

@vbezhenar posted a link to Apple Support in his comment: https://support.apple.com/en-us/HT201191

right at the top, if you scroll past “27-inch” you’ll see this gem: “*Memory is not removable by users on iMac (21.5-inch, Late 2012), iMac (21.5-inch, Late 2013), iMac (21.5-inch, Mid 2014), iMac (21.5-inch, 2017), and iMac (Retina 4K, 21.5-inch, 2017). If the memory in one of these computers needs repair service, contact an Apple Retail Store or Apple Authorized Service Provider.”

i call this the “iMac pitfall”.

I don’t think so - but you used to have to separate the screen from the base of the computer which while very doable was much more involved than popping open a case and inserting an additional stick of of ram