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What Does My Hard Drive Model Number Mean?

Portrait of Devin ChuaBy Devin Chua · Data checked by Owen Nakamura · Updated
Try: · · · ·
FieldValueConfidence
MakerWestern DigitalManufacturer documentation
Capacity8 TBConsistent across the models we checked
Form factor3.5 inchConsistent across the models we checked
LineWD Red PlusManufacturer documentation
RecordingCMRManufacturer documentation
In short

Paste a drive model number to read back its capacity, product line and, where the maker has stated it, whether the drive uses conventional or shingled recording. We read Western Digital, Seagate, Toshiba and Ultrastar numbers. Anything we cannot verify is reported as unknown rather than guessed.

The formula

Western Digital  WD + capacity + unit letter + 4-character line suffix
                 the final capacity digit is a tenth: WD80 = 8.0 TB, WD201 = 20.1 TB (sold as 20 TB)

Seagate          ST + capacity in GB + 2-letter segment + 3 attribute digits + generation
                 ST16000NM001G = 16000 GB, NM = Exos nearline

Toshiba          MG/MN + generation + ACA + capacity + T/G + suffix (capacity stated)
                 HDWG/HDWD consumer codes do NOT encode capacity

Ultrastar        WUH/HUH + platform block + interface and sector code (ALE600 = SATA 512e)
Capacity is not decoded for Ultrastar or for Toshiba's consumer HDW codes, because the digit groups do not follow one rule across generations. Printing a plausible number there would be worse than leaving it out.

Worked examples

Each example is the function this page runs, with the inputs shown. A test asserts these results still match the code.
CaseInputsWorkingResult
WD Red PlusWD80EFPX80 -> 8.0, E = TB/3.5in, EFPX = Red Plus (CMR)8 TB, WD Red Plus, CMR
The SMR oneWD40EFAX40 -> 4.0, EFAX = Red, SMR at 2 to 6 TB4 TB, WD Red, SMR
Seagate nearlineST16000NM001G16000 GB, NM = Exos16 TB, Exos, CMR

Why a model number is worth decoding

The model number is the only identifier that travels with a drive. A retail listing may describe a drive as "NAS grade" or "8TB internal" without ever saying which product it is, and two drives in the same family at the same capacity can use different recording technology. The number printed on the label settles it, and it is the thing you can check against a datasheet.

The question people usually arrive with is whether a drive uses conventional or shingled recording. That distinction matters because shingled drives overlap tracks to gain density and pay for it on rewrite: a RAID rebuild or a sustained random write can slow by an order of magnitude. For an array this is the difference between a drive that works and one that causes a resilver to take days.

How each maker encodes its drives

Western Digital uses a structured scheme: the company prefix, a capacity figure carrying one decimal place, a letter for the unit and form factor, then a four-character suffix identifying the product line. WD80EFPX is 8.0 TB, 3.5-inch, Red Plus. The suffix is where the useful information sits, and it is the part most listings omit.

Seagate is the most readable of the four: capacity is stated literally in gigabytes, followed by a two-letter segment code. ST16000NM001G is 16,000 GB in the Exos nearline family. Toshiba splits into two schemes, one that states capacity and one that does not. Ultrastar numbers encode a platform block whose capacity digits do not follow a single rule across generations.

What this decoder will not tell you

Ultrastar capacity and Toshiba consumer capacity are deliberately left blank, because no single rule covers them and a plausible wrong answer is worse than no answer. The Backblaze data bears this out: a WUH721816ALE6L4, which looks like an 18 TB part from its platform block, is actually 16 TB. Had the decoder guessed, it would have been wrong on a drive thousands of people own.

Every rule carries a confidence level and a link to where it came from, so you can see whether an answer rests on manufacturer documentation or on consistency across the models we checked. Anything we cannot place returns "not in our decoder yet" rather than a guess.

Questions

Is my WD Red an SMR drive?

Only the EFAX suffix at 2, 3, 4 and 6 TB. WD published that list in 2020 after the disclosure controversy. EFAX at 8 TB and above is conventional recording, and every Red Plus and Red Pro suffix is conventional at every capacity.

Why does the decoder say 20.1 TB for a 20 TB drive?

Western Digital encodes capacity with one decimal place, so WD201 is 20.1. Drives in that range are sold as 20 TB. We show the sold capacity and note the encoded figure rather than silently picking one.

Why will it not tell me the capacity of my Ultrastar?

The digit pairs in an Ultrastar platform block do not follow a single rule across generations, so any capacity we derived would be a guess. The label and the datasheet both state it plainly.

What does the suffix after the dash mean?

On Western Digital drives that trailing block is for internal inventory use and the maker has never published a key. We ignore it rather than invent meanings for it.

Does a model number tell me the warranty?

No. The line implies the warranty term the maker advertises, but the actual cover depends on the manufacturing date and whether the drive was sold bare or inside an enclosure. Check the serial number against the maker's own warranty tool.

Sources