How to Choose an M.2 SSD for a Laptop

What to check, in order

• Connector/key type — M.2 drives use a notch position (commonly "M key" for NVMe, "B+M key" for some SATA drives) that must match the slot.
• Physical length — expressed as a 4-digit code (e.g. 2280 = 22mm wide, 80mm long). A drive that's the wrong length simply won't fit, even with the correct connector.
• Interface — NVMe (PCIe) and SATA M.2 drives are electrically different; a slot that's wired for one won't necessarily run the other, even if the connector fits.
• PCIe generation — a newer, faster-generation drive will still work in an older-generation slot, but runs at the slot's maximum speed rather than the drive's rated maximum.

Length codes you'll commonly see

2230 and 2242 are compact sizes used in some thin-and-light and handheld devices; 2280 is the most common laptop size. Always check your laptop's documented supported length(s) before buying — a drive that's too long for the slot cannot be forced to fit.

Capacity

Unless the manufacturer explicitly documents a maximum supported capacity for a slot, there generally isn't a hard capacity ceiling beyond what the connector/form-factor/interface allow — don't assume a laptop that originally shipped with a 512 GB drive is limited to 512 GB; check the documented maximum instead of inferring one from the original configuration.