What are all the differences between the "Late 2015" Aluminum iMac models and the models replaced?

Please note that the "Late 2015" iMac models have been discontinued. However, this Q&A has been updated subsequently and can be quite helpful to anyone buying or selling one of these systems on the used market.

On October 13, 2015, Apple introduced the "Late 2015" iMac models -- the iMac "Core i5" 1.6 21.5-Inch, "Core i5" 2.8 21.5-Inch, "Core i5" (4K) 3.1 21.5-Inch, and "Core i7" 3.3 (4K) 21.5-Inch -- with 21.5-Inch displays -- and the iMac "Core i5" 3.2 (5K) 27-Inch, "Core i5" 3.3 (5K) 27-Inch, and "Core i7" 4.0 (5K) 27-Inch -- with 27-Inch displays.

These models thankfully replaced a motley mess of systems first introduced in "Late 2013" -- the iMac "Core i5" 2.7 21.5-Inch, "Core i5" 2.9 21.5-Inch, "Core i7" 3.1 21.5-Inch, and "Core i5" 3.2 27-Inch; "Mid-2014" -- the iMac "Core i5" 1.4 21.5-Inch; "Late 2014" -- the iMac "Core i5" 3.5 27-Inch and "Core i7" 4.0 27-Inch -- and "Mid-2015" -- the Mac "Core i5" 3.3 27-Inch -- all of which were sold at the same time.

Because the "Late 2015" iMac models replace so many different earlier systems, sorting out the differences can be complicated and an evaluation can be particularly helpful as a result.

Photo Credit: Apple, Inc. (Late 2015 iMac Models)

External & Connectivity Differences

The 21.5-Inch and 27-Inch models from all of these lines use essentially the same all aluminum case design that tapers sharply to a 5 mm edge at the sides of the display and each have an integrated 720p "FaceTime HD" webcam in the upper display bezel, speakers integrated at the bottom edge of the display, and dual integrated microphones.

However, although all have a glass cover and an anti-reflective coating, the displays themselves are quite different.

21.5-Inch models in the "Late 2013" and "Mid-2014" iMac lines have a 1920x1080 LED-backlit 16:9 widescreen IPS display, as do the entry-level "Late 2015" models -- the iMac "Core i5" 1.6 21.5-Inch and "Core i5" 2.8 21.5-Inch -- whereas the the iMac "Core i5" (4K) 3.1 21.5-Inch and "Core i7" 3.3 (4K) 21.5-Inch -- have a much higher-quality 21.5" 4096x2304 LED-backlit 16:9 widescreen IPS DCI-P3 "Retina 4K" display that runs "pixel doubled."

Likewise, the 27-Inch models in the "Late 2013" line have a 27" 2560x1440 LED-backlit 16:9 widescreen IPS display, the "Late 2014/Mid-2015" Retina 5K models have a 27" LED-backlit 16:9 widescreen IPS display with a massive 5120x2880 resolution running "pixel doubled," and the "Late 2015" models also have a display with the same 5120x2880 resolution, but it's an even higher-quality IPS DCI-P3 panel, with much better color gamut support, although it still may not be good enough for some professional photographers.

Connectivity is similar across the lines -- all of these models have an SDXC-capable SD card slot, four USB 3.0 ports, one Gigabit Ethernet port (10/100/1000Base-T), one "headphone/optical digital audio output (minijack)" that also supports the Apple iPhone headset with microphone, as well as Bluetooth 4.0 and 802.11ac Wi-Fi -- but the "Late 2013" models have two Thunderbolt ports whereas all later models have two Thunderbolt 2 ports.

None of these models have an integrated optical drive, although an external one may be added at additional cost. Site sponsor Adorama has the official external Apple SuperDrive for US$79 and Other World Computing has a variety of third-party external optical drive options that may be of interest.

All of these models shipped with a notebook size aluminum wireless keyboard without a numeric keypad. Earlier systems shipped with a choice of either the wireless "Magic Mouse," the "Magic Trackpad," or a traditional wired Apple mouse and the "Late 2015" models offered the choice of either a multi-touch "Magic Mouse 2" or a traditional wired Apple mouse. For an additional US$50, one also could upgrade from the Magic Mouse 2 to the "Magic Trackpad 2," which provides multi-touch and pressure-sensitive "Force Touch" capabilities.

Identification Differences

All of these iMac lines share Model Numbers. Specifically, the 21.5-Inch systems share model number A1418 and the 27-Inch systems share model number A1419. Consequently, these identifiers are not useful for most tasks.

However, these systems can be differentiated by Model Identifier in software and EMC Number externally. Just as the site has for all other Macs for many years, EveryMac.com has meticulously hand documented all of these details for your convenience:

iMac Model	Model ID	EMC No.
iMac "Core i5" 2.7 21.5-Inch (Late 2013)	iMac14,1	2638
iMac "Core i5" 2.9 21.5-Inch (Late 2013)	iMac14,3	2742
iMac "Core i7" 3.1 21.5-Inch (Late 2013)	iMac14,3	2742
iMac "Core i5" 3.2 27-Inch (Late 2013)	iMac14,2	2639
iMac "Core i5" 3.4 27-Inch (Late 2013)	iMac14,2	2639
iMac "Core i7" 3.5 27-Inch (Late 2013)	iMac14,2	2639
iMac "Core i5" 1.4 21.5-Inch (Mid-2014)	iMac14,4	2805
iMac "Core i5" 3.5 27-Inch (5K, Late 2014)	iMac15,1	2806
iMac "Core i7" 4.0 27-Inch (5K, Late 2014)	iMac15,1	2806
iMac "Core i5" 3.3 27-Inch (5K, Mid-2015)	iMac15,1	2806
iMac "Core i5" 1.6 21.5-Inch (Late 2015)	iMac16,1	2889
iMac "Core i5" 2.8 21.5-Inch (Late 2015)	iMac16,2	2889
iMac "Core i5" 3.1 21.5-Inch (4K, Late 2015)	iMac16,2	2833
iMac "Core i7" 3.3 21.5-Inch (4K, Late 2015)	iMac16,2	2833
iMac "Core i5" 3.2 27-Inch (5K, Late 2015)	iMac17,1	2834
iMac "Core i5" 3.3 27-Inch (5K, Late 2015)	iMac17,1	2834
iMac "Core i7" 4.0 27-Inch (5K, Late 2015)	iMac17,1	2834

Additionally, EveryMac.com's Ultimate Mac Lookup feature also can identify each of these iMac models by their serial numbers.

Internal Differences

Internally, these models have massive differences from one another. In general terms, though, the 21.5-Inch models are slower, have slower graphics, and are either more difficult or impossible to upgrade internally than the 27-Inch models available at the same time.

For example, it is needlessly difficult to upgrade the RAM in the "Late 2013" models, but altogether impossible to upgrade the RAM in later 21.5-Inch models after initial system purchase as the RAM is soldered in place. By contrast, all of these 27-Inch models offer RAM upgrades via a convenient door on the rear of the system. Processors also are soldered in all of these 21.5-Inch models, but are socketed for the 27-Inch ones.

Architectures are similar for earlier systems -- "Late 2013", "Mid-2014", "Late 2014" and "Mid-2015" all are based on Haswell -- but the "Late 2015" models use the newer Broadwell and Skylake architectures for the 21.5-Inch and 27-Inch models, respectively.

Comparison Charts

The major differences between the 21.5-Inch "Late 2013", "Mid-2014" and "Late 2015" Aluminum iMac models are summarized below. Please refer to the specs page for the model of interest for complete details.

21.5-Inch "Late 2013," "Mid-2014" and "Late 2015" iMac Differences

	21.5" iMac (Late 2013)	21.5" iMac (Mid-2014)	21.5" iMac (Late 2015)	4K 21.5" iMac (Late 2015)
Processor Speed:	2.7 GHz, 2.9 GHz*	1.4 GHz	1.6, 2.8 GHz	3.1 GHz**
Processor Type:	Quad Core i5*	Dual Core i5	Dual/Quad Core i5	Quad Core i5
Processor Family:	Haswell	Haswell ULT	Broadwell	Broadwell
Processor Mounting:	Soldered	Soldered	Soldered	Soldered
RAM Type:	1600 MHz PC3-12800 DDR3	1600 MHz LPDDR3 SDRAM	1867 MHz LPDDR3 SDRAM	1867 MHz LPDDR3 SDRAM
Standard RAM:	8 GB	8 GB	8 GB	8 GB
Maximum RAM:	16 GB	8 GB	16 GB†	16 GB†
RAM Slots:	2	None	None	None
RAM Upgrade:	Difficult (Hack)	Soldered	Soldered	Soldered
Standard Storage:	1 TB	500 GB	1 TB	1 TB
PCIe SSD Connector:	Yes	No	No	No
Standard Graphics:	Iris Pro 5200 GeForce GT 750M	HD Graphics 5000	HD Graphics 6000 Iris Pro 6200	Iris Pro 6200
VRAM Type:	Integrated 1 GB (GDDR5)	Integrated	Integrated	Integrated
Display Size:	21.5-Inch	21.5-Inch	21.5-Inch	21.5-Inch
Display Resolution:	1920x1080	1920x1080	1920x1080	4096x2304
Thunderbolt:	Dual (1.0)	Dual (2.0)	Dual (2.0)	Dual (2.0)
Order Number (US):	ME086LL/A, ME087LL/A	MF883LL/A	MK142LL/A MK442LL/A	MK452LL/A
EMC Number:	2638, 2742	2805	2889	2833
Model Identifier:	iMac14,1, iMac14,3	iMac14,4	iMac16,1 iMac16,2	iMac16,2
Original Price (US):	US$1299 US$1499	US$1099	US$1099 US$1299	US$1499
Original Price (UK):	£1149 £1299	£899	£899 £1049	£1199
Original Price (CA):	C$1349 C$1549	C$1149	C$1399 C$1649	C$1899
Original Price (AU):	A$1599 A$1849	A$1349	A$1699 A$1999	A$2299

* The ME087LL/A configuration of the "Late 2013" system additionally could be equipped with a 3.1 GHz Quad Core "Core i7" processor (I7-4770S) for an extra US$200. EveryMac.com also has documented this custom configuration as its own model.

** By custom configuration, the iMac "Core i5" (4K) 3.1 21.5-Inch could be configured with a 3.3 GHz Quad Core "Core i7" processor (I7-5775R) for an extra US$200. EveryMac.com also has documented this custom configuration as its own model.

† In these models, 8 GB of RAM is onboard. They could be upgraded to 16 GB at the time of purchase as an optional upgrade for US$200. The RAM cannot be upgraded later at all.

27-Inch "Late 2013," "Late 2014," "Mid-2015" and "Late 2015" iMac Differences

The major differences between the standard 27-Inch "Late 2013," "Late 2014," "Mid-2015" and "Late 2015" Aluminum iMac models are summarized below. Please refer to the specs page for the model of interest for complete details:

	27" iMac (Late 2013)	27" iMac (Late 2014)	27" iMac (Mid-2015)	5K 27" iMac (Late 2015)
Processor Speed:	3.2 GHz, 3.4 GHz*	3.5 GHz**	3.3 GHz	3.2, 3.3 GHz†
Processor Type:	Quad Core i5*	Quad Core i5**	Quad Core i5	Quad Core i5†
Processor Family:	Haswell	Haswell	Haswell	Skylake
Processor Mounting:	LGA 1150	LGA 1150	LGA 1150	LGA 1151
Standard RAM:	8 GB	8 GB	8 GB	8 GB
Maximum RAM:	32 GB	32 GB	32 GB	64 GB
RAM Slots:	4	4	4	4
RAM Upgrade:	Easy (Door)	Easy (Door)	Easy (Door)	Easy (Door)
Standard Storage:	1 TB (Hard Drive)	1 TB (Fusion)	1 TB (Hard Drive)	1 TB (HD, Fusion) 2 TB (Fusion)
Standard Graphics:	GeForce GT 755M GeForce GTX 775M	Radeon R9 M290X	Radeon R9 M290	Radeon R9 M380/M390 Radeon R9 M395
Dedicated VRAM:	1 GB (GDDR5) 2 GB (GDDR5)	2 GB (GDDR5)	2 GB (GDDR5)	2 GB (GDDR5)
Display Size:	27-Inch	27-Inch	27-Inch	27-Inch
Display Resolution:	2560x1440	5120x2880	5120x2880	5120x2880
Thunderbolt:	Dual (1.0)	Dual (2.0)	Dual (2.0)	Dual (2.0)
Order Number (US):	ME088LL/A, ME089LL/A	MF886LL/A	MF885LL/A	MK462LL/A MK472LL/A MK482LL/A
EMC Number:	2639	2806	2806	2834
Model Identifier:	iMac14,2	iMac15,1	iMac15,1	iMac17,1
Orig. Price (US):	US$1799 US$1999	US$2499	US$1999	US$1799 US$1999 US$2299
Orig. Price (UK):	£1599 £1749	£1999	£1599	£1449 £1599 £1849
Orig. Price (CA):	C$1849 C$2049	C$2749	C$2399	C$2299 C$2599 C$2999
Orig. Price (AU):	A$2199 A$2449	A$2999	A$2799	A$2799 A$3099 A$3599

* This system originally could be configured with a 3.5 GHz Quad Core "Core i7" processor (I7-4771) for an extra US$200, as well. EveryMac.com also has documented this custom configuration as its own model.

** The "Late 2014" model additionally could be configured with a 4.0 GHz Quad Core "Core i7" processor (I7-4790K) for an extra US$250. EveryMac.com also has documented this custom configuration as its own model.

† The higher-end configuration of the iMac "Core i5" 3.2 (5K) 27-Inch (MK472LL/A) as well as the iMac "Core i5" 3.3 (5K) 27-Inch additionally could be configured with a 4.0 GHz Quad Core "Core i7" processor (I7-6700K) for an extra US$300 or US$250, respectively. EveryMac.com also has documented this custom configuration as its own model.

Comparison Summary

Ultimately, the "Late 2015" iMac models represented a significant step forward for the iMac line, both in terms of hardware specifications and marketing cohesiveness.

All of these 21.5-Inch models, unfortunately, are more difficult to upgrade than they need to be, and later models are actually worse than the earlier "Late 2013" systems, but the "Late 2015" line at least gains the option of a beautiful, high-resolution display.

Just compared to one another, the 27-Inch "Late 2015" iMac models are the top choice for anyone interested in a sleek, beautiful, and upgradable all-in-one Mac. Of course, given even lower prices on the used market, older models remain well worth consideration, too.

Used iMac Purchase Options

There are many places to purchase a used Mac from 2013, 2014, or 2015 alike. However, purchasing from a quality company with an established history in the Mac market -- and after sales support -- is the best option and will save you money and time, too.

In the US, site sponsor Adorama sells new iMac models with free shipping. Other World Computing sells used and refurb iMac models at bargain prices with free shipping, as well. Finally, if you need to sell an iMac, A+ BBB-rated Cash for Your Mac will buy your older iMac with an instant quote and prompt payment.

In the UK, site sponsor Hoxton Macs sells used iMac models with a one-year warranty and free next day delivery throughout the UK. Delivery across Europe also is available starting at just £9.99 for two-day delivery to France and Germany.

Please also see EveryMac.com's Ultimate Mac Comparison feature to dynamically compare any iMac model to any other Mac.