Apple SSDs Explained — MacBook, iMac & Mac Pro Storage

If you've come here trying to work out what SSD is in your Mac — what type it is, how fast it should be, whether you can upgrade it, or whether you can rescue data from it after a failure — this article covers every Apple SSD from the 2012 Retina onwards through the current M4 generation. We've worked on every one of these at the bench, and the answers vary a lot depending on which Mac you've got.

The headline you need to know upfront: from 2018 onwards, Apple soldered the SSD directly to the logic board. Before that, most Macs had a removable proprietary blade SSD you could upgrade. After it, the storage is part of the motherboard. That's the single biggest fact that changes what's possible for upgrades, replacements, and data recovery.

The four eras of Apple SSDs (and what they mean)

Apple uses four distinct generations of proprietary SSD across the 2012-2017 removable era, plus a fifth bracket for the soldered era from 2018 onwards. These aren't standard M.2 — they're Apple-specific connectors that won't fit any other computer. Generation defines the connector shape, the protocol (SATA vs PCIe), and the maximum speed.

Gen 2 (7+17 pin, SATA III): The MacBook Air 2010-2017 and MacBook Pro Retina mid-2012 to early-2013. Two-row connector, SATA III protocol, real-world speeds around 500 MB/s. Still common in workshop trade-ins; OWC and other third parties still make replacement modules.

Gen 3 (12+16 pin, PCIe 2.0 x2): MacBook Pro Retina late-2013 through mid-2015. Apple moved off SATA and onto PCIe at this point, which is where SSDs first started genuinely feeling fast — real-world speeds jumped to around 1,400 MB/s. Different connector shape from Gen 2; the two are not interchangeable.

Gen 4 (12+16 pin, PCIe 3.0 x4): MacBook Pro Retina late-2015, MacBook Pro Touch Bar 2016-2017, MacBook 12-inch 2015-2017, iMac 2017-2020. Same physical 12+16 pin connector as Gen 3 but quadrupled the PCIe bandwidth. Real-world reads near 2,000 MB/s. Most third-party upgrade modules target this connector because the Gen 4 era is where high-performance upgrades make economic sense.

Gen 5 / soldered NAND (PCIe 3.0/4.0): The 2018+ Intel MacBook Pro, all M-series MacBooks (M1, M2, M3, M4), current Apple Silicon iMacs, and current Mac mini. There is no removable SSD module — the NAND flash chips are soldered directly to the logic board. Speeds range from 1,500 MB/s on the base M2 Air up to 7,400 MB/s on higher-capacity M3 Pro/Max MacBook Pros. Generationally, Apple Silicon uses a custom storage controller built into the SoC rather than a separate Apple SSD controller chip.

How to identify which SSD is in your Mac

The easiest way is the model identifier. On the Mac, click the Apple menu, About This Mac, and find the line that gives you the year and screen size — for example "MacBook Pro (Retina, 15-inch, Mid 2015)" or "MacBook Pro (15-inch, 2018)". Match that to the era list above and you've got your generation.

The mid-2012 to early-2013 Retinas are Gen 2 (SATA). Late-2013 through mid-2015 are Gen 3 (PCIe 2.0 x2). Late-2015 Retina is Gen 4 (PCIe 3.0 x4). The 2016-2017 Touch Bar generation kept the Gen 4 connector for one more cycle. From 2018 onwards, every MacBook has its storage soldered to the board and the question of "which generation" becomes about NAND chip count and SoC capability rather than connector type.

The MacBook Air is similar — 2010-2017 used blade modules across Gen 2 and Gen 4. From 2018 onwards (the Retina MacBook Air with Touch ID), storage is soldered. On iMacs, 2017-2020 27-inch and 21.5-inch had Gen 4 blade modules; everything from the M1 iMac (2021) onwards is soldered.

When Apple moved to soldered storage — and why it matters

The 2018 transition is the single most important year in this story. Before 2018, almost every Mac had user-replaceable storage. From 2018 onwards, almost none of them do. Apple's stated reason was thermal performance and tighter SoC-to-storage integration. The real-world consequences for owners are significant.

Upgradability disappeared overnight. A 2017 MacBook Pro with a 256GB SSD could be upgraded to 1TB by anyone with a Torx screwdriver and an OWC module. A 2018 MacBook Pro with a 256GB SSD is stuck at 256GB forever — there is no upgrade path at any price, at any service centre, including Apple's. Apple's "upgrade" path is buying a new Mac with more storage from the factory.

Data recovery also changed completely. Before 2018, recovering data from a dead Mac was as simple as removing the SSD module and reading it from another machine or an external adapter. After 2018, if the logic board dies, your data is sitting on NAND chips physically attached to that dead board. Recovery requires microsoldering the chips off the board (chip-off recovery), mounting them on a donor board or a specialised chip-reader, and reading them that way. It's possible — we do this work — but it's a different category of service from "swap the SSD module out."

Encryption matters too. From 2018 onwards (and especially on Apple Silicon), every Mac has a hardware security chip (T2 on Intel, Secure Enclave inside the SoC on Apple Silicon) that encrypts the SSD at the hardware level using a key tied to that specific board. Even if you successfully read the raw NAND chips, the data is encrypted with a key that lives on a different chip. Recovery is only possible if either (a) the Secure Enclave chip is still alive on the original board, or (b) you have FileVault recovery credentials. Without one of those, the data is permanently encrypted from anyone — including Apple.

Upgrade options — what's actually possible

If you've got a pre-2018 Mac with a removable SSD, upgrades are straightforward. For Gen 2 (SATA) modules, OWC's Aura line and similar third-party brands offer drop-in replacements up to 2TB. For Gen 3 and Gen 4 (PCIe blade) modules, OWC's Aura Pro X2 is the most commonly recommended upgrade, available up to 4TB. Installation is half an hour with the right pentalobe and Torx drivers.

M.2 NVMe adapters also exist for the Gen 3 and Gen 4 connectors. These are small interposer boards that let you plug a standard M.2 SSD into the Apple blade slot. They work fine but the performance is gated by the older PCIe generation of the Mac itself, so a modern PCIe 4.0 M.2 NVMe SSD won't run any faster in a Gen 4 Mac than a properly-binned Gen 4 module would.

For post-2018 MacBooks, MacBook Airs, and current iMacs, there is no upgrade path. The storage is part of the board. The only way to "get more storage" is to either use external storage (Thunderbolt 3/4 SSDs are fast enough to feel native), use iCloud, or replace the entire computer with a higher-capacity model.

Mac Pro storage is its own category. The 2019 Intel Mac Pro and the 2023 M2 Ultra Mac Pro have proprietary storage modules in pairs (sold by Apple only, at Apple prices) — technically removable, technically upgradable, but tied to Apple's own modules and the T2 / Secure Enclave pairing on that specific tower.

Got an older MacBook with a removable blade SSD that's running out of space? We fit OWC and Apple-pulled upgrade SSDs at the bench in Erina. Call (02) 4311 6146 or book a slot online — same-day fittings most weeks.

How fast are Apple SSDs really?

Apple publishes peak sequential read figures that look impressive on a spec sheet. Real-world performance is often slower, sometimes substantially, because peak numbers are measured under ideal conditions that don't match how you actually use a computer.

The base-model M2 MacBook Air controversy from 2022 is a good example. Apple specified the same "up to 2,800 MB/s" read speed for both 256GB and 512GB+ variants, but benchmarks showed the 256GB base model running at half that speed — around 1,500 MB/s. The reason was that Apple had cost-reduced the 256GB SKU by using a single 256GB NAND chip instead of two 128GB chips in parallel. Modern flash storage gets most of its speed from running multiple chips simultaneously; with only one chip, half the parallelism, half the speed. The same trick appeared on the base M2 MacBook Pro 13-inch.

Higher-capacity M-series MacBook Pros are genuinely fast — 7,400 MB/s sequential read on a current M3 Max with 1TB+ storage. But sustained writes (continuous large file transfer) are still lower than peak reads, and random small-file I/O (which is what most actual computer usage looks like) is lower again. The day-to-day difference between a fast SSD and a very fast SSD is usually smaller than spec sheets suggest.

When SSDs fail — and what we can recover

SSDs fail differently from mechanical drives. Mechanical hard drives degrade gradually — they get slower, develop bad sectors, click, and eventually stop spinning. SSDs more often fail abruptly. The drive works fine, then one day the Mac won't boot, and the SSD isn't visible to Disk Utility either. The most common failure modes we see are firmware corruption, controller chip failure, and (less often) bad NAND flash blocks accumulating past the firmware's ability to remap.

On older removable-SSD Macs, recovery is generally straightforward. We pull the SSD module, mount it in an external adapter, and either image it directly or attempt firmware-level recovery via specialised hardware. Success rate is high for Gen 2/3/4 modules.

On post-2018 soldered-SSD Macs, recovery is significantly more involved. The NAND chips are physically soldered to the logic board, so we have to remove them via microsoldering (the chip-off process), mount them on either a donor logic board or a specialised chip-reader rig, and read them from there. We can do this, but two things have to be true for the data to come back: the NAND chips themselves have to be intact (not damaged by the same event that killed the board), and either the T2/Secure Enclave on the original board is still functional for pairing, or FileVault recovery credentials are available, or the disk was not encrypted (rare on post-2018 Macs).

If you've got a dead Mac and the data matters, more detail on what's possible is in our data recovery article. For liquid-damaged MacBooks specifically (a common cause of soldered-SSD recovery jobs), our MacBook liquid damage repair article covers that path. The shortest version: bring it to us before trying anything yourself, and the sooner the better.

iMac and Mac Pro storage specifics

The iMac story tracks the MacBook story with a one-year lag. Fusion Drive iMacs from 2012-2016 had a small flash SSD on a separate module paired with a 1TB or 3TB mechanical hard drive in a logical "fused" volume — these can be split back to SSD-only by reformatting, though Apple's Fusion firmware is fussy about it. The 2017-2020 27-inch and 21.5-inch iMacs use Gen 4 blade SSDs and are upgradable with effort (the iMac has to be disassembled by separating the screen from the chassis — the SSD is replaceable but it's not a quick job). The M1 iMac (2021), M3 iMac (2023), and M4 iMac (2024) all have soldered storage with no upgrade path.

Mac Pro is the outlier. The 2019 Intel Mac Pro and 2023 M2 Ultra Mac Pro both have removable proprietary SSD modules in pairs, but they're sold only by Apple, priced at Apple's storage tier rates ($600+ per upgrade), and they're paired to the specific tower's T2 chip — you can't move modules between Mac Pros. So technically upgradable, practically constrained.

Common questions