SSD upgrade on 2017 iMac 21.5

Skill level: "advanced"; Professional installation recommended.

https://eshop.macsales.com/installvideos/imac-21-inch-2017-main-drive/

https://eshop.macsales.com/installvideos/imac-21-inch-2017-pcie_ssd/

It would be much easier and less expensive to do an external SSD.

If you go the external SSD route I would suggest one of these from OWC (MacSales.com):

Envoy Pro EX with USB-C or USB 3 - best from a speed vs price standpoint

OWC Envoy Pro EX with Thunderbolt 3 - fastest if you have a Thunderbolt 3 port but more expensive

I suggest you contact the excellent OWC Customer Support and find out which would be best for your particular iMac model.

If you're having performance issues, we need an EtreCheck report. EtreCheck is a useful App to diagnose and identify issues, both hardware and software. It is trusted by many users. Please follow the steps outlined below:

1. Navigate to: https://etrecheck.com and get the free version of EtreCheckPro.
2. Download it. It is a free and trusted app. It is often recommended here on Apple Support Communities. 
3. Open EtreCheck, and before running the report, be sure to check “Allow full Drive Access” at the bottom of the EtreCheckPro window.
4. Run the report, and put it in a post, as seen here: https://discussions.apple.com/docs/DOC-250000211. We will then examine the report for issues in your Mac.

Cheers,

Jack

I would go and get a external SSD. I have not done it but have considered doing so! I have the same year and 21.5 as you do check out this article it gives you strep by step on how to boot an external SSD! https://www.macworld.com/article/339485/a-fusion-macs-speed-getting-you-down-give-it-a-boost-with-an-external-ssd.html

If you’re set on upgrading to an SSD, use an external SSD instead. For more info, instructions, and what external SSD to buy, read: https://discussions.apple.com/docs/DOC-250003583.

Cheers,

Jack