M.2 is a form factor for SSDs (solid-state drives) that’s shaped like a stick of gum. Most M.2 SSDs are 80 x 22mm (L x W), but they can be shorter or longer. You can tell what size an M.2 SSD is by reading the four or five-digit number in its name: the first two numbers are its width, while the others are its length (example: M.2 Type-2280). Thin laptops are increasingly using M.2 SSDs because they take up less room than traditional, 2.5-inch SATA drives.
M.2 SSDs go up to 2TB in storage size. Other form factors offer more capacity.
While 2.5-inch SSDS use the Serial ATA (SATA) bus, which debuted in 2000 and was originally geared toward hard drives, and add-in cards use the PCIe bus, which is faster and has more bandwidth than SATA, M.2 SSDs can go either way, depending on the product.
Additionally, some of the fastest SSDs use the NVMe interface, which was made for rapid storage devices. So an M.2 SSD can be SATA-based, PCIe-based with NVMe support, or PCIe-based without NVMe support. An M.2 SSD with NVMe support offers up to five times more bandwidth than SATA models, bringing better performance in key tasks such as file transfers, video or photo editing, transcoding, compression and decompression.
This article is part of the Tom's Hardware Glossary.