imac 18.2 ram upgrade

+1 on rkaufmann87's very important question.

About 95% of slow 21.5-iMac reports here have nothing to do with RAM but everything to do with the slow, under-spec laptop drives Apple opted to install between 2012 and 2019. THey are 2.5-inch 5400rpm, SATA 3GB drives on a fast 6GB SATA drive bus. A simple three-question test will help:

1. Is the computer slow to boot?
2. Are apps very slow to launch?
3. Once launched, do the apps seen to run fine?

Three "YES" answers say you have the same slow factory drive as thousands of other posters here. This issue tend to get worse as you install progressively newer macOS versionw ith more capabilities but a bigger load on resources.

The Mac OS is super-efficient with RAM management; it can sdo wonders with only 8GB RAM for most consumer tasks. If you have a slow factory mech drive, your can throw all the RAM in Crucial at the problem and not improve it.

You can increase the RAM up to 64GBs. However, the RAM in a 21.5" iMac is non user-accessible since you have to tear it completely apart. You should find an Apple Authorized Service Provider willing to do it.

The real question is why do you feel you need so much RAM?

I have 12 GB RAM in my late 2009 iMac (easy user accessible on that model) and it is more than enough indeed. Even for photoshopping and all