Computers · SELECTION GUIDE
TLC or QLC SSD? Memory type is only part of the picture
TLC stores three bits per cell and QLC stores four. The controller, cache and your workload also matter when choosing an SSD.
Published 1 October 2026 · Source-based comparison
Do not choose or reject a drive solely because it uses TLC or QLC. Check the exact model, capacity, write endurance and how much data you write in one go.
Editorial assessment, not our own product test.Differences side by side
| Comparison point | TLC NAND | QLC NAND |
|---|---|---|
| Bits per cell | 3 | 4 |
| What to check | Model, capacity and write workload | Model, capacity and write workload |
| What the label alone cannot tell you | The actual speed of the complete SSD | The actual speed of the complete SSD |
| Useful additional information | TBW rating and sustained-performance tests | TBW rating and sustained-performance tests |
Product specifications are manufacturer claims. Figures in standards comparisons are not measured real-world results. Conclusions depend on how you use the device.
A technology label is not a product ranking
Memory type describes how the cells store data. The controller, firmware and cache affect the drive as a whole. If a manufacturer only states '3D NAND', that does not reliably tell you whether it is TLC or QLC.
Large writes need a different kind of test
A brief peak-speed figure does not tell you how long that speed can be sustained. If you often transfer large projects, look for an independent test using a long, continuous write. Compare the same capacity.
A second copy is your best protection
A drive can fail regardless of its memory type. Keep a separate backup and check that you can restore it. A TBW rating is no reason to assume valuable files are safe in only one location.
Three checks before buying
- Confirm the memory type in the manufacturer's specifications, if it is disclosed.
- Do not assume tests of a different capacity apply to your drive.
- Check the TBW rating and warranty conditions.
Frequently asked questions
Is 3D NAND the same as TLC?
No. 3D describes a layered structure; TLC describes the number of bits stored per cell.
Is QLC always a bad choice?
No. Assess the complete product, your workload and the current price.
Sources and limitations
This guide uses the manufacturer or standards sources listed below, gathered for this content on 1 October 2026. We have not tested the products ourselves. Usage recommendations are editorial assessments. We do not maintain live prices or stock information.