This is the single most confused topic in computer storage, and it costs people money every day. Someone buys an "M.2 SSD" expecting blazing NVMe speed, fits it, and wonders why it is no faster than the drive it replaced. Or worse, it does not fit at all.
Here is the thing that clears it up: M.2 is a shape, not a speed.
The Three Things That Get Mixed Up
Form factor is the physical shape and connector. This is 2.5-inch, or M.2, or mSATA.
Interface is how the drive connects to the system electrically. This is SATA or PCIe.
Protocol is the language the drive speaks. This is AHCI (used by SATA) or NVMe (used over PCIe).
People treat "M.2" and "NVMe" as the same word. They are not. An M.2 drive can be SATA or NVMe, and the difference in speed is enormous.
The Types You Will Actually Meet
2.5-inch SATA SSD. The flat rectangular one that looks like a small hard drive. Connects with a SATA data cable and power. Caps out around 550MB/s. Still a massive upgrade over a mechanical drive, and still the only option in a lot of older laptops.
M.2 SATA SSD. Looks like a stick of gum. Slots directly into the motherboard. Despite the modern shape, it is still running the SATA interface, so it is still limited to roughly 550MB/s. Same speed as the 2.5-inch drive, just a smaller package.
M.2 NVMe SSD. Same gum-stick shape, but running over PCIe using the NVMe protocol. This is where the speed is. Gen3 drives run around 3,500MB/s. Gen4 drives run around 7,000MB/s. Several times faster than anything SATA can do.
So two drives that look physically identical can differ in speed by a factor of six or more. That is why "it is an M.2" tells you nothing useful on its own.
How to Tell Them Apart: The Notches
Look at the connector edge of the drive. The notches, called keying, tell you what it is.
M key has a single notch positioned toward one side. This is typically NVMe.
B+M key has two notches. This is typically SATA.
It is not a perfect rule, but it is a solid first check. Crucially, the keying also determines what will physically slot in. A B+M keyed SATA drive will often fit into an M keyed NVMe socket, but it will only work if the socket supports SATA. Some sockets are NVMe only.
The Numbers on the Drive: 2280 and Friends
You will see codes like 2242, 2260, 2280 and 22110. These are dimensions in millimetres.
The first two digits are the width, which is almost always 22mm. The rest is the length. So 2280 means 22mm wide and 80mm long, which is the most common size by far.
This matters. Your laptop's M.2 slot has mounting points at specific lengths. A 2280 drive will not fit a machine that only accommodates 2242. Check before you buy.
The Trap: A Slot That Only Does SATA
Here is the one that catches people out most.
Some laptops, particularly older or budget models, have an M.2 slot that only supports SATA. You put an NVMe drive in it and nothing happens. The drive does not show up, the machine does not see it, and you assume the drive is faulty. It is not. The slot simply cannot speak NVMe.
The reverse also happens. A newer machine may have an NVMe-only slot that will not recognise an M.2 SATA drive.
This is why "it is an M.2 slot so any M.2 drive works" is wrong, and why it is worth checking before ordering.
How to Check What Your Machine Takes
Check the manual or spec sheet for your exact model. Look for the words NVMe, PCIe, SATA, and the supported length.
Open it and look. If there is already a drive in there, read the label. It will tell you the type and the size.
Use your model number. Give us your exact laptop model and we can tell you what it takes. Our guide on finding your laptop model number covers how to get that if you are not sure.
The Practical Summary
If your machine supports NVMe, buy NVMe. The price gap has narrowed a lot and the speed difference is real, especially for boot times and loading large files.
If your machine only supports SATA, a SATA SSD is still a huge upgrade over a mechanical hard drive. Do not feel short-changed.
And whatever you buy, confirm three things before you order: the interface your slot supports, the keying, and the physical length. Get those right and it will work first time.
Not sure what your laptop takes? Send us your model number and we will confirm the right drive type and size before you order.
