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iMac (Retina 4K, 21.5-inch, 2017) vs iMac (21.5-inch, Late 2015)

iMac (Retina 4K, 21.5-inch, 2017)1iMac (21.5-inch, Late 2015)2

Quick look

Quick look: iMac (Retina 4K, 21.5-inch, 2017) against iMac (21.5-inch, Late 2015)
FigureiMac (Retina 4K, 21.5-inch, 2017)1iMac (21.5-inch, Late 2015)2
Price£1,2493launch price£8994launch price
ChipCore i53.0GHz quad-core IntelCore i51.6GHz dual-core Intel
CPU4-coreCPU2-coreCPU
Memory8GBmemory, base8GBmemory, base
Storage1TBstorage, base1TBstorage, base
Display21.5-inchdisplay21.5-inchdisplay
Released7 June 20173ReleasedIn Apple Stores; orderable online from 5 June 2017.13 October 20154Released
Security updates15 September 20255Security updates ended16 September 20245Security updates ended
Price
The iMac (Retina 4K, 21.5-inch, 2017) is £1,249 at launch, per Apple Newsroom (UK); the iMac (21.5-inch, Late 2015) is £899 at launch, per Apple Newsroom (UK).

True to scale

iMac (Retina 4K, 21.5-inch, 2017) · 528 × 450 mm frontiMac (21.5-inch, Late 2015) · 528 × 450 mm front

Front faces, from Apple’s published dimensions, drawn to one scale and superposed. Corner rounding is our drawing convention, not a measurement.

Specifications

Each figure is from the source marked by its Mac’s name unless it carries its own small number, which links to where that figure was read.

Body

Body: Apple iMac (Retina 4K, 21.5-inch, 2017) against Apple iMac (21.5-inch, Late 2015)
SpecificationiMac (Retina 4K, 21.5-inch, 2017)1iMac (21.5-inch, Late 2015)2
Dimensions450 x 528 x 175 mm450 x 528 x 175 mm
Weight5.66 kg5.68 kg
PortsTwo Thunderbolt 3 (USB-C) ports, four USB 3 ports, SDXC card slot, Gigabit Ethernet (RJ-45), 3.5 mm headphone jackTwo Thunderbolt 2 ports, four USB 3 ports, SDXC card slot, Gigabit Ethernet (RJ-45), 3.5 mm headphone jack
Thunderbolt ports622
Thunderbolt versionThunderbolt 3Thunderbolt 2
USB-A ports44
HDMINo HDMI port.7No HDMI port.8
SD card slotYesYes
Headphone jackYesYes
KeyboardMagic KeyboardMagic Keyboard
Touch IDNo Touch ID.7No Touch ID.8

Display

Display: Apple iMac (Retina 4K, 21.5-inch, 2017) against Apple iMac (21.5-inch, Late 2015)
SpecificationiMac (Retina 4K, 21.5-inch, 2017)1iMac (21.5-inch, Late 2015)2
Display size21.5 in21.5 in
Resolution4096 x 23041920 x 1080
Display typeRetina 4K displayLED-backlit display with IPS technology
Brightness500 nitsNot available9
Wide colour (P3)YesNot available9

Chip and memory

Chip and memory: Apple iMac (Retina 4K, 21.5-inch, 2017) against Apple iMac (21.5-inch, Late 2015)
SpecificationiMac (Retina 4K, 21.5-inch, 2017)1iMac (21.5-inch, Late 2015)2
Chip3.0GHz quad-core Intel Core i51.6GHz dual-core Intel Core i5
Apple siliconIntel processor, not Apple silicon.10Intel processor, not Apple silicon.11
CPU cores42
GraphicsRadeon Pro 555 with 2GB of VRAMIntel HD Graphics 6000
Chip options3.0GHz quad-core Intel Core i5, 3.4GHz quad-core Intel Core i5, or 3.6GHz quad-core Intel Core i71.6GHz dual-core Intel Core i5 or 2.8GHz quad-core Intel Core i5
Memory (base)8GB8GB
Memory (maximum)32GB16GB
Memory options8GB, 16GB or 32GB8GB or 16GB
Memory upgradeable by userNo, as Apple documents12No, as Apple documents12
Storage (base)1TB1TB
Storage (maximum)1TB2TB
Storage options1TB hard drive, 1TB Fusion Drive, or 256GB, 512GB or 1TB SSD1TB hard drive, 1TB or 2TB Fusion Drive, or 256GB flash storage (SSD)

Connectivity

Connectivity: Apple iMac (Retina 4K, 21.5-inch, 2017) against Apple iMac (21.5-inch, Late 2015)
SpecificationiMac (Retina 4K, 21.5-inch, 2017)1iMac (21.5-inch, Late 2015)2
Wi-Fi802.11ac Wi-Fi802.11ac Wi-Fi
Bluetooth4.24.0
Ethernet10/100/1000BASE-T Gigabit Ethernet (RJ-45)10/100/1000BASE-T Gigabit Ethernet (RJ-45)
External displays (base)21

Camera and audio

Camera and audio: Apple iMac (Retina 4K, 21.5-inch, 2017) against Apple iMac (21.5-inch, Late 2015)
SpecificationiMac (Retina 4K, 21.5-inch, 2017)1iMac (21.5-inch, Late 2015)2
CameraFaceTime HD cameraFaceTime HD camera
SpeakersStereo speakersStereo speakers
MicrophonesMicrophoneDual microphones

Platform

Platform: Apple iMac (Retina 4K, 21.5-inch, 2017) against Apple iMac (21.5-inch, Late 2015)
SpecificationiMac (Retina 4K, 21.5-inch, 2017)1iMac (21.5-inch, Late 2015)2
Shipped withNot available13OS X El Capitan14
Newest macOSmacOS Ventura15macOS Monterey15
Model identifieriMac18,215iMac16,115
Model year20172015

Sources

  1. Apple Support (UK) — iMac (Retina 4K, 21.5-inch, 2017) - Technical Specifications · Default for iMac (Retina 4K, 21.5-inch, 2017) · Apple’s figure · read 15 Sep 2026

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  2. Apple Support (UK) — iMac (21.5-inch, Late 2015) - Technical Specification · Default for iMac (21.5-inch, Late 2015) · Apple’s figure · read 15 Sep 2026

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  3. Apple Newsroom (UK) — iMac receives major update featuring more powerful graphics, faster processors, Thunderbolt 3 and brighter displays · Apple’s figure · read 15 Sep 2026

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  4. Apple Newsroom (UK) — Apple Updates iMac Family with Stunning New Retina Displays · Apple’s figure · read 15 Sep 2026

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  5. endoflife.date — Apple macOS · third-party figure · read 2 Oct 2026

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  6. Different Thunderbolt generations. iMac (Retina 4K, 21.5-inch, 2017): Thunderbolt 3. iMac (21.5-inch, Late 2015): Thunderbolt 2.

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  7. iMac (Retina 4K, 21.5-inch, 2017): No HDMI port. No Touch ID. Checked: Apple Support (UK) — iMac (Retina 4K, 21.5-inch, 2017) - Technical Specifications. Read 9 Oct 2026

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  8. iMac (21.5-inch, Late 2015): No HDMI port. No Touch ID. Checked: Apple Support (UK) — iMac (21.5-inch, Late 2015) - Technical Specification. Read 9 Oct 2026

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  9. Not published by Apple. Pages checked: Apple Support (UK) — iMac (21.5-inch, Late 2015) - Technical Specification; Apple Support (UK) — Identify your iMac model; Apple Newsroom (UK) — Apple Updates iMac Family with Stunning New Retina Displays. Read 9 Oct 2026

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  10. iMac (Retina 4K, 21.5-inch, 2017): Intel processor, not Apple silicon. Checked: Apple Support (UK) — iMac (Retina 4K, 21.5-inch, 2017) - Technical Specifications. Read 15 Sep 2026

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  11. iMac (21.5-inch, Late 2015): Intel processor, not Apple silicon. Checked: Apple Support (UK) — iMac (21.5-inch, Late 2015) - Technical Specification. Read 15 Sep 2026

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  12. Apple Support (UK) — Install memory in an iMac · Apple’s figure · read 18 Oct 2026

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  13. Not published by Apple. Pages checked: Apple Support (UK) — iMac (Retina 4K, 21.5-inch, 2017) - Technical Specifications; Apple Support (UK) — Identify your iMac model; Apple Newsroom (UK) — iMac receives major update featuring more powerful graphics, faster processors, Thunderbolt 3 and brighter displays. Read 9 Oct 2026

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  14. Apple Newsroom (UK) — Apple Updates iMac Family with Stunning New Retina Displays · Apple’s figure · read 9 Oct 2026

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  15. Apple Support (UK) — Identify your iMac model · Apple’s figure · read 15 Sep 2026

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Not published by Apple

iMac (Retina 4K, 21.5-inch, 2017). Apple doesn’t publish for this Mac: colours, pixel density, refresh rate, nano-texture option, GPU cores, storage upgradeable by user, maximum continuous power. Geekbench 7 Metal: the Mac chart has no Metal score for this Mac (chart read 10 Oct 2026). Pages checked: Apple Support (UK) — iMac (Retina 4K, 21.5-inch, 2017) - Technical Specifications; Apple Support (UK) — Identify your iMac model; Apple Newsroom (UK) — iMac receives major update featuring more powerful graphics, faster processors, Thunderbolt 3 and brighter displays, read 9 Oct 2026.

iMac (21.5-inch, Late 2015). Apple doesn’t publish for this Mac: colours, pixel density, refresh rate, nano-texture option, GPU cores, storage upgradeable by user, maximum continuous power. Geekbench 7: the Mac chart has no entry for this Mac, so no figures are shown (chart read 10 Oct 2026). Pages checked: Apple Support (UK) — iMac (21.5-inch, Late 2015) - Technical Specification; Apple Support (UK) — Identify your iMac model; Apple Newsroom (UK) — Apple Updates iMac Family with Stunning New Retina Displays, read 9 Oct 2026.

If you own one of them

Whether to move is a different question from which is better. Each Mac has a page on it: what its successor changes (the newest Mac in its line where Apple sells one, otherwise the Mac this site treats as its replacement, which can be in another line), what it fetches and whether it still gets updates. Should I upgrade my iMac (Retina 4K, 21.5-inch, 2017)? · Should I upgrade my iMac (21.5-inch, Late 2015)?

The pairs a buyer of either Mac would also weigh. Any two Macs in the catalogue can be compared from the chooser.