M.2 Key Compatibility Guide
Compare M.2 Keys A, B, E, M and dual-key cards. Check mechanical fit, common interfaces, limits, and detailed pinout references.
Essential rule: matching notches only confirm mechanical fit. The socket must also provide the protocol, lane count, power, sideband signals, and firmware support required by the module.
Quick compatibility table
| Card key | Typical socket fit | Common use / interfaces | Important limit | Pinout |
|---|---|---|---|---|
| A | Key A, Socket 1 | Wireless, PCIe x1, USB 2.0, DisplayPort | Host wiring varies | Key A |
| A+E | Key A or E, Socket 1 | Wi-Fi and Bluetooth, PCIe x1, USB 2.0 | Fit does not guarantee CNVi or interface support | Key A+E |
| B | Key B, Socket 2 | WWAN, SATA, USB, PCIe up to x2 | Not every Key B socket provides every protocol | Key B |
| B+M | Key B or M | SATA SSD or PCIe storage up to x2 | Does not gain PCIe x4 in a Key M socket | Key B+M |
| E | Key E, Socket 1 | Wi-Fi, Bluetooth, PCIe x1, USB 2.0 | CNVi/CNVio requires a compatible platform | Key E |
| M | Key M, Socket 3 | NVMe PCIe up to x4 or SATA | Protocol support must match the SSD | Key M |
| B+A | May clear Key B or A | Custom card or test adapter | Non-standard; A and B pinouts conflict | Key B+A |
| B+E | May fit Key B or E | Custom card or test adapter | Non-standard; B and E pinouts conflict | Key B+E |
Before installation
- Match the card notch to the socket key.
- Confirm the required protocol: PCIe/NVMe, SATA, USB, or platform-specific connectivity.
- Check PCIe lane count, power rails, sideband signals, BIOS support, and module length.
- Power the equipment down before inserting or removing the module unless hot plugging is explicitly supported.