Apple iMac 21.5-inch 4K Review

Apple packs plenty of power in this compact all-in-one desktop computer

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Apple iMac 21.5-inch 4K

Apple iMac 21.5-inch 4K

Lifewire / Gannon Burgett

What We Like
  • Beautiful 4K display

  • Compact and lightweight

  • Minimal setup required

What We Don't Like
  • Difficult to replace RAM, HDD

  • A bit pricey

Apple knows a thing or two about creating beautiful all-in-one desktop computers and its latest 21.5-inch 4K iMac is no exception. It offers capable hardware wrapped in a sleek, beautiful frame with a gorgeous 4K display.


Apple iMac 21.5-inch 4K

Apple iMac 21.5-inch 4K

Lifewire / Gannon Burgett

We purchased the Apple iMac 21.5-inch 4K so our expert reviewer could thoroughly test and assess it. Keep reading for our full product review.

Apple is no stranger to creating minimal devices, but the 21.5-inch 4K iMac takes things to a whole new level with a screen that pops and a design that looks stylish no matter the setting. As beautiful as it is on the outside, under the hood you also have a solid set of components with a 3.4GHz 7th generation quad-core Intel Core i5 CPU, 8GB RAM, and 1TB Fusion Drive. Apple has managed to pack quite a bit of power inside the slender frame. We put it to the test to see how it fares for multimedia and productivity uses.

Apple iMac 21.5-inch 4K
Lifewire / Gannon Burgett

Design: Beautiful, with room for improvements

It shouldn’t come as a surprise that the Apple iMac 21.5-inch 4K is a beautiful machine from top to bottom. Before even turning it on, the design of the computer a striking, aluminum-clad body that’s still subtle enough that it will blend in with nearly any office or home environment.

The tapered design makes the edges appear almost non-existent while its bulkier behind manages to round things out in a proportional manner. At its thinnest point — the edges — the iMac measures in at just 0.2 inches. On its integrated stand, the iMac measures in at 17.7 inches tall, 20.8 inches wide, and 6.9 inches deep. Amazingly, all of that weighs in at just 12.5 pounds, not including the keyboard and mouse.

Overall, the 21.5-inch 4K iMac is a solid all-in-one computer that packs a lot of power into a tiny, well-designed package.

Aside from the Apple logo on the front aluminum chin of the iMac, all of the connections and ports on the iMac are on the rear of the computer. This includes, left to right: a 3.5mm headphone jack, SD card slot, four USB 3.0 ports, two Thunderbolt 3.0 ports (USB-C), a Gigabit Ethernet port, and power adapter. There’s also a Kensington lock slot to let you secure the the iMac. 

We would’ve liked to see a thinner bezel around the screen, as the one present on the iMac is about half an inch — much larger than even the most basic PC monitors. It’d be a bit different if Apple were doing more with that real estate, but as it stands, it feels like wasted space

Apple iMac 21.5-inch 4K
Lifewire / Gannon Burgett

Setup Process: One plug and you’re good to go

One of Apple’s core tenets is simplicity, and the 4K iMac is no exception to this rule. Inside the box is the computer itself and a box which contains the Magic Keyboard and Magic Mouse 2. Additional components include the power connection for the computer, a Lightning cable for charging the mouse and keyboard, and a small package of documentation.

Setting up the iMac is as simple as unwrapping it from its protective cover, setting it on the desk, plugging it in with the included power cord, and pressing the power button. As it boots up, we turned on the Magic Keyboard and Magic Mouse 2. By the time the iMac was to the setup screen — a process that took approximately 60 seconds — the two were already paired with the computer and ready to be used.

Going through the setup process took us approximately five minutes, which included setting up our iCloud account and getting the various login settings in place. We opted to set this up as a new computer, but there’s also the ability to set it up from an Apple Time Capsule backup or transfer content from a PC via USB. The amount of time those options take will vary depending on the device you’re transferring the information from as well as the amount of data being transferred.

Display: Bright, brilliant, and ready to shine

With a resolution of 4096 x 2304 pixels, the 4K iMac has more than 9.4 million pixels and features a pixel density of 217 pixels per inch, more than enough to make individual pixels indistinguishable at normal viewing distances. Text was clear across nearly every application and browser and photos just came to life with ridiculous levels of detail.

The brightness, contrast, and clarity of the screen are stunning. The display can show more than one billion colors and features a wide color gamut. Apple rates the brightness at 500 nits and our testing confirmed that to be the case.

With a resolution of 4096 x 2304 pixels, the 4K iMac has more than 9.4 million pixels and features a pixel density of 217 pixels per inch

As mentioned above, it would’ve been nice to see a smaller bezel, but that’s about the only department the display falls short.

Apple iMac 21.5-inch 4K

Lifewire / Gannon Burgett

Performance: Impressive performance from an all-in-one

Our particular iMac model for this review was the 3.4GHz quad-core Intel Core i5 iMac with 8GB of RAM and a 1TB Fusion Drive.

Before diving into the benchmark specs we achieved with this computer, we’ll first explain what a Fusion Drive is. Unlike a traditional hard drive (HDD), which relies exclusively on spinning platters to write and read information, Apple’s Fusion Drive also adds a small solid state storage (SSD) partition. This is where the operating system and most critical applications are stored, as solid state memory is much faster than traditional HDDs. The result is a drive that offers some of the advantages of SSDs while still offering the more affordable price tag and capacity of HDDs.

In our tests, boot-up time ranged from 15 seconds to 25 seconds. Considering the hybrid-style Fusion Drive, this lines up with our expectations, falling right between SSD speeds and HDD speeds. The same held true with boot-up times for various applications, ranging from Safari to more resource-intensive applications such as Final Cut Pro.

Moving onto the CPU and GPU benchmarks, we tested the iMac with both Geekbench and Cinebench to see how well the 3.4GHz quad-core processor and AMD Radeon Pro 560 held up.

“Could you build a PC with better specs for far less money? Absolutely. But it won’t be running macOS and it certainly won’t be as slim and streamlined as the iMac.”

In the Geekbench tests, the iMac scored 4,866 on the single core test, 14,151 on the multi-core test, and 56,974 on the OpenCL score. This falls in line with other iMacs of the same specifications and hovers around other computers with similar specifications. In Cinebench, the iMac achieved 93.86 frames per second in the OpenGL test and a score of 584 cb in the CPU test.

All-in-all, the iMac seems to punch right at or above its specifications when compared to similar hardware. It’s not going to be pumping out 8K footage, but for basic 4K video editing and image post-processing, the graphics card is more than enough. As for productivity, there’s not much you can throw at the iMac that it can’t handle. The only thing we noticed slowing down the computer was the 8GB of RAM when we had over a dozen applications open, but that can be fixed by upgrading to the 16GB or 32GB model (although it’s not a cheap upgrade).

Network: Fast and reliable

The 21.5-inch 4K iMac features both wired and wireless connectivity for internet access. As previously mentioned, the iMac features a Gigabit Ethernet (RJ-45) port on the rear of the computer for a hardwired internet connection. For Wi-Fi, the iMac uses an 802.11ac network adapter with support for IEEE 802.11a/b/g/n.

In our hardwired tests, the iMac maxed out our Gigabit fiber optic internet no problem, with steady download and upload speeds. Wireless connectivity was equally impressive, regardless of whether the iMac was in the same room as the router or a few rooms over. We didn’t notice any drops throughout our tests and both uploading and downloading content was consistent.

Camera: Decent built-in option for basic tasks

The only camera on the 4K iMac is the integrated webcam, which sits dead center above the display. We would’ve liked to see a 1080p or even 4K webcam included, but the 720p resolution is good enough for basic video messaging.

Apple iMac 21.5-inch 4K
Lifewire / Gannon Burgett

Software: Everything you need and nothing more

As with all Apple computers, the 21.5-inch 4K iMac comes with macOS Mojave pre-installed. If you’re used to macOS as a whole, you’ll feel right at home as we did. Compared to past versions of macOS, Mojave improves in a number of areas, including an integrated Dark mode that turns much of the user interface dark grey to spare your eyes. There’s also a feature called “Stacks” that intelligently combines files of the same type on your desktop. Improved screenshot functionality also makes snapping your screen easier.

One of the stand-out benefits of macOS is that you’ll never have to worry about paid upgrades. Apple annually announces and subsequently releases a new operating system, free of charge, to install on Apple computers. In-between major releases Apple will also push out incremental updates, at least two of which we installed during our review process. These incremental installs can be done either manually within the System Preferences applications or be set to install themselves automatically when the computer is plugged in and powered on.

Unlike Windows, macOS doesn’t come with any bloatware either. There’s a number of pre-installed apps developed by Apple, including four new ones borrowed from Apple’s mobile operating system, iOS, but most of the pre-installed apps are the standard array of programs you’d expect to see on any modern computer.

Price: The Apple tax is real

The 21.5-inch 4K iMac we tested with the aforementioned specifications retails for $1,499. Compared to other Windows PCs with similar specifications, the iMac is without pricey for the specs it offers. However, this is par for the course with Apple, so much so that the term “Apple tax” has become a commonly-used phrase. What you’re paying for is the entire package, wrapped up in one of the best-looking frames out there.

Could you build a PC with better specs for far less money? Absolutely. But it won’t be running macOS and it certainly won’t be as slim and streamlined as the iMac. If you’re invested in the Apple ecosystem and don’t need to shell out for the more expensive 27-inch 5K iMac, the 21.5-inch 4K iMac is priced much more reasonably and still has plenty to offer.

Competition: A unique option in a small market

The 21.5-inch 4K iMac has a few competitors in its specification range, but for the sake of simplicity, we’ll focus on two: the Lenovo IdeaCentre AIO 700 and the Asus Zen AiO Pro Z240IC.

All three all-in-one desktops feature 4K displays (or at least the option to order them with 4K displays). Aside from that, the specifications also line up similarly, with i7 CPU configurations, dedicated GPU options, SSD variations, and beefy memory choices.

Of course, the biggest difference between the three desktops is that the 21.5-inch 4K iMac runs macOS while the other two run Windows 10. Using Apple’s included Boot Camp program, it’s possible to run Windows 10 (and other operating systems) on the iMac, but macOS isn’t able to be run on the other devices.

Other differences include various connections options on the back of the computers and variations in size—most notably the iMac is quite a bit smaller in dimensions across the board. That said, the larger size allows easier access to internals which makes upgrading easier on the Lenovo Ideacentre AIO 700 and Asus Zen AiO Pro Z240IC.

Prices vary greatly between the three desktops depending on the configuration you’re looking for, but overall, the 21.5-inch 4K iMac seems to hold its own in this price range, despite Apple’s notoriety for being a little bit on the pricier side.

Final Verdict

Beautiful display in a thin, powerful machine.

The 21.5-inch 4K iMac is a solid all-in-one computer that packs a lot of power into a tiny, well-designed package. It’s not going to blow anyone away on benchmarks and it’s not cheap for the internal components you’re getting, but it has a lot to offer for multimedia and productivity. That’s not to mention the sheer convenience of having everything simply work out of the box.

Similar Products We've Reviewed:


  • Product Name iMac 21.5-inch 4K
  • Product Brand Apple
  • UPC 190198085795
  • Price $1,499.00
  • Weight 12.5 lbs.
  • Product Dimensions 17.7 x 20.8 x 6.9 in.
  • Platform Windows 10 Home
  • CPU 3.6GHz quad-core Intel Core i5
  • GPU Raden Pro 560
  • RAM 8GB
  • Storage 1TB Fusion Drive
  • Connections 3.5 mm headphone jack, SDXC card slot, Four USB 3 ports (compatible with USB 2), Two Thunderbolt 3 (USB-C) ports, 10/100/1000BASE-T Gigabit
  • What’s in the box 21.5‑inch iMac with Retina 4K display Magic Keyboard Magic Mouse 2 Power cord Lightning to USB Cable
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