M.2 (pronounced “M dot 2”) is a compact hardware form factor: a small circuit-board module and matching connector used for expansion devices, most commonly solid-state drives (SSDs) and wireless cards. M.2 describes the shape and connector. It does not tell you how data moves. An M.2 SSD may use SATA or PCIe, and the drive, the socket and the host system all have to support the same protocol before the drive will work.
What M.2 actually specifies
M.2 defines the physical module: its length and width, the position of the notch that keys it into a socket, and the edge connector that mates with the host board. Kingston Technology’s FAQ says the specification was developed by PCI-SIG and SATA-IO, the two groups that also maintain the PCIe and SATA standards. Because M.2 sits on top of those standards rather than replacing them, the same physical slot can carry different electrical signals depending on what the drive and the host agree to use.
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That distinction explains most of the confusion around the term. Calling a drive “M.2” tells you the size and connector. It does not tell you whether the drive is SATA or PCIe, and it does not tell you whether the drive uses the NVMe storage protocol.
Shape versus interface
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- Form factor: M.2 describes the module’s dimensions and connector. Two M.2 drives can look identical and still differ in interface.
- Interface: SATA or PCIe is the electrical link between the drive and the host. Kingston’s FAQ states the rule plainly: “An M.2 SSD will support either SATA or PCIe, but not both at the same time.” The statement is an official vendor position on the FAQ page; the page names no individual author and gave no publication date in the source reviewed.
- Protocol: NVMe is a storage protocol associated with PCIe SSDs. It is not a synonym for M.2, and an M.2 drive is not NVMe merely because it fits an M.2 slot.
The interface figures and what they measure
Kingston Technology’s FAQ lists the maximum throughput of each link type. These are interface ceilings, not measured results for any particular drive. The year of the FAQ was not stated in the version reviewed.
| Link type (as listed by Kingston Technology) | Stated maximum | What the figure means |
|---|---|---|
| SATA 3.0 | 600 MB/s | Interface limit only |
| PCIe Gen 2 x2 | 1,000 MB/s | Interface capability only |
| PCIe Gen 2 x4 | 2,000 MB/s | Interface capability only |
| PCIe Gen 3 x4 | 4,000 MB/s | Interface capability only |
A drive’s real speed depends on its controller, memory, workload and thermal behavior, so a higher interface ceiling does not guarantee a faster drive. A PCIe ceiling is also only reachable if the socket actually provides that many lanes to the drive.
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Reading the size code
M.2 sizes are written as four digits. The first two give the module width in millimeters, which is 22 mm for every size Kingston lists. The remaining digits give the length in millimeters.
| Size code | Width | Length |
|---|---|---|
| 2230 | 22 mm | 30 mm |
| 2242 | 22 mm | 42 mm |
| 2260 | 22 mm | 60 mm |
| 2280 | 22 mm | 80 mm |
| 22110 | 22 mm | 110 mm |
A longer drive will not fit a shorter socket, but a shorter drive can often sit in a longer slot. Check the mounting screw position as well, since it is fixed at a particular point along the board.
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Other things M.2 carries
M.2 is not limited to storage. Kingston’s FAQ lists other module types that use the same form factor: Wi-Fi, Bluetooth, satellite navigation, NFC, digital radio, WiGig and wireless WAN cards. A slot labeled M.2 on a motherboard or laptop may therefore hold a wireless card rather than a drive, so confirm which function the slot is designed for.
Where the name NGFF fits
You will still see “NGFF” in older documentation. Kingston says M.2 was formally renamed from “Next Generation Form Factor” in 2013. NGFF and M.2 refer to the same form factor, so an NGFF drive or slot is a matter of naming rather than a different standard.
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Checking compatibility before you buy
- Open the motherboard or laptop manual and find the M.2 slot section. Note which protocols the slot supports (SATA, PCIe, or both) and which module types it accepts.
- Confirm the socket’s key position and the maximum module length the slot takes, such as 2280.
- Read the drive’s listing for its interface (SATA or PCIe) and its size code. Do not rely on the M.2 label or the notch alone.
- Check whether the slot shares PCIe lanes or SATA ports with other devices. Kingston notes that some sockets do, and a sharing conflict can disable one device when another is installed.
- If the manual is unclear, treat the slot’s stated protocol as the limit. A drive that fits physically may still be unsupported electrically or by the system’s configuration.
Why the definition matters
The word M.2 answers a physical question: will the module fit the connector? The interface answers a different question: will the drive talk to the host at the speed you expect? A correct purchase needs both answers. The manufacturer’s FAQ is a reliable source for definitions and for the interface figures above, but it is a product document rather than an independent performance test, and the system’s own manual remains the final authority for what a given socket accepts.
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