How much RAM can the 27-inch iMac (2020) take, and is it user-upgradeable?

The 27-inch iMac (2020) takes up to 128GB of user-upgradeable DDR4 RAM via four accessible SO-DIMM slots on a rear RAM door. It’s one of Apple’s most user-friendly designs, letting you buy base RAM from Apple and upgrade later with cheaper off-the-shelf kits.