How to Upgrade RAM in a 2019 iMac 27-Inch — Fast and Easy
Apple makes a lot of decisions about what you can and can’t upgrade on your own hardware. The 2019 27-inch iMac is a pleasant exception — it ships with a user-accessible RAM panel right on the back of the machine, no tools required to open it. Apple even put a little button there. And yet most people who buy one of these at the base 8GB configuration never touch it.
This post covers how I upgraded mine from 8GB to 32GB using an OWC kit, and why I should have done it on day one.
Why I bought 8GB in the first place
The 2019 iMac 27-inch was a significant purchase — the 27-inch Retina 5K screen, i5 processor, the works. I use it every single day for video editing, and it’s the best computer I’ve ever owned. But I bought the base memory configuration because it was already expensive and I figured 8GB would be enough.
It wasn’t. Specifically: whenever I’m working with picture-in-picture elements, multiple tracks, or importing a lot of different media in iMovie or Final Cut Pro, the thing will just crash. Not often — but often enough that I started researching whether there was a simple fix. There was.
What the 2019 iMac 27 uses
The 27-inch iMac (2019) takes DDR4 SO-DIMM modules running at 2666 MHz (PC4-21300). There are four slots — Apple ships the base model with two 4GB sticks in two of those slots, leaving two empty. The maximum supported capacity is 64GB (4 × 16GB), though OWC has certified kits up to 128GB using 32GB modules.
The key word here is “user-accessible.” Apple explicitly supports end-user RAM upgrades on this machine. The panel is designed to be opened. This is in stark contrast to basically every other Mac in the lineup for the past several years, where RAM is soldered directly to the board and can’t be changed at all.
What I bought
I picked up an OWC 32GB kit — two 16GB DDR4 SO-DIMMs — for about $138. That brings the total to 40GB (keeping the original two 4GB sticks installed) or a clean 32GB if you pull the originals. I left mine in and went to 40GB total.
OWC is the name in Mac memory upgrades. Their kits are specifically tested against Apple machines, come with a lifetime warranty, and they’ve been doing this since before most people had heard of RAM upgrades. If you’re going to spend money on third-party memory for an Apple machine, OWC is the safe choice.
The install
Open the panel — it’s on the back of the machine, at the bottom. There’s a small button just above the power connector. Press it and the RAM door pops right out. No screwdriver needed.
You’ll see the existing RAM sticks in the slots. There are two small tabs at each end of each slot — pressing those simultaneously releases the stick and pops it up at an angle so you can grab it. For the new sticks, just align the notch on the module with the key in the slot, slide it in at about a 30-degree angle, and press down until both tabs click.
The door goes back on the same way it came off. That’s genuinely it — I’d done it before it felt like I’d barely started. The whole thing took maybe five minutes, including time to locate a towel to lay the machine on.
After booting, open About This Mac and the new total shows up immediately.
The result
40GB of RAM, and the video editing crashes stopped. Final Cut Pro in particular noticeably snappier when I’m working with complex timelines. If you use your iMac for anything memory-intensive — video editing, running virtual machines, keeping forty Chrome tabs open — the upgrade is worth every penny.
The gotcha
The 2019 27-inch is the last Intel iMac that has user-upgradeable RAM. The M1 and M2 iMac models that came after it use unified memory soldered to the chip — you configure it at purchase and that’s it forever. If you’re considering a used 2019 or 2020 27-inch iMac, the fact that you can upgrade the RAM yourself later is a genuine selling point worth factoring into your decision.
What you’ll need
- OWC (or compatible) DDR4 SO-DIMM 2666 MHz modules — 8GB, 16GB, or 32GB sticks depending on your target capacity. The machine supports mixed capacities.
- A soft surface (towel, cloth) to lay the iMac face-down on while you work
- About five minutes
That’s it. No screwdrivers, no heat guns, no spudgers. Apple built this upgrade to be done by the user and made it legitimately easy.