QLC NAND (quad-level cell) is a type of flash memory that stores four bits of information in each memory cell. This allows manufacturers to pack more data into the same physical space, bringing down the cost per gigabyte compared to faster alternatives like SLC, MLC, or TLC NAND.
How it works: each cell can hold 16 different electrical states (2 to the power of 4), representing the four bits. Because the states are closer together, the controller must work harder to read and write data accurately, which means QLC is generally slower than TLC and requires more sophisticated error correction.
Common uses include budget consumer SSDs, external drives, and USB flash drives where raw speed takes a back seat to capacity and affordability. You'll find QLC in many entry-level NVMe drives and SATA SSDs aimed at general computing, photo storage, and media libraries.
Real-world example: a 1TB QLC SSD might cost noticeably less than a 1TB TLC drive, but you may notice slightly longer load times in demanding applications. For everyday tasks like browsing, document editing, and video playback, the difference is rarely noticeable.
When buying, check whether a drive uses QLC, especially if you plan heavy video editing or gaming. If speed matters, TLC is worth the extra spend. If you want maximum storage for your money and can live with modest performance, QLC delivers good value.