Degaussing: 20 Questions, Answered Plainly.

What is degaussing?

Degaussing erases magnetic storage by exposing it to a strong magnetic field. The field scrambles the magnetic domains on the platters or tape, so the recorded data can no longer be read. It works in seconds and needs no power to the drive.

Can a hard drive be used after degaussing?

No. A properly degaussed hard drive cannot be used again. The same field that erases your data also erases the servo tracks written at the factory, which the read and write heads need to find their position. Without them the drive cannot operate, and it cannot be repaired with ordinary equipment.

Why does a degaussed drive stop working?

Hard drives store more than your data on the platters. Servo tracks guide the heads, and part of the drive's firmware lives in a reserved area of the platters too. Degaussing wipes all of it. The drive may spin up, but it cannot identify itself or read anything.

Can SSDs be degaussed?

No. SSDs, including NVMe drives, store data as electrical charge in flash memory cells, not as magnetic patterns. A degausser has no effect on the data. SSDs must be erased with firmware commands such as NVMe Sanitize or crypto erase, or physically shredded.

What cannot be degaussed?

Anything that does not store data magnetically: SSDs and NVMe drives, USB flash drives, SD and microSD cards, the built-in storage in phones and tablets, eMMC storage in thin laptops, CDs, DVDs and Blu-ray discs, and paper. Hybrid drives (SSHDs) have a small flash cache that degaussing will not clear.

What can be degaussed?

Hard disk drives, magnetic backup tapes such as LTO and DLT, floppy disks, older audio and video tapes, and magnetic stripe cards.

Does degaussing physically damage the hard drive?

Not visibly. A degaussed drive looks exactly like a working one. That is why many policies follow degaussing with shredding or crushing, and why serial numbers must be recorded before degaussing.

Why must serial numbers be recorded before degaussing?

After degaussing, the drive can no longer report its own serial number electronically. The only record is the printed label. A proper certificate lists serials captured before the drive entered the degausser.

Is degaussing enough on its own?

NIST SP 800-88 Rev. 2 still lists degaussing as a purge technique for magnetic media, but only when the degausser is rated for the drive's coercivity. It warns that a drive can stop working without its data being fully erased, and it does not count degaussing as destruction. That is why many organisations follow degaussing with shredding, and why US NSA guidance for classified hard drives pairs degaussing with physical damage.

How strong does a degausser need to be?

Stronger than the media's coercivity, which is its resistance to being re-magnetised. Modern high-density drives have much higher coercivity than older ones, so an old degausser may not be rated for them. Check the rating against the drive type. The NSA/CSS Evaluated Products List publishes degaussers that have been tested.

Can data be recovered from a degaussed hard drive?

Not by any practical means, if a degausser rated for that drive was used. The data is not hidden behind the missing servo tracks; the magnetic patterns that held it have been scrambled. With an under-powered degausser, a drive can stop working while some data survives on the platters, which is why the degausser rating matters and why shredding afterwards is common.

How long does degaussing take?

A few seconds per drive for the degaussing itself. Recording serials, loading and logging take longer than the pulse.

What happens if you put a laptop or phone in a degausser?

The SSD or flash storage inside keeps its data, so the data is not destroyed. Magnetic parts such as speakers can be damaged. Laptops and phones need a different method: remove and shred the storage, or use a verified firmware erase.

Can a fridge magnet or the drive's own magnets erase a hard drive?

No. Household magnets are far too weak, and the magnets inside a drive are part of the head actuator and are designed not to affect the platters. Only an industrial degausser produces a strong enough field.

Can you degauss LTO backup tapes?

Yes. Degaussing erases the tape, and on LTO it also destroys the servo tracks, so the cartridge cannot be reused. Newer LTO generations use barium ferrite particles with high coercivity, so the degausser must be rated for them.

Is degaussing better than shredding?

They do different jobs. Degaussing erases magnetic media quickly but leaves the drive intact, and it does nothing to SSDs. Shredding destroys every media type and gives visible proof. For mixed batches, the usual answer is degauss magnetic media, then shred everything that needs physical destruction.

Is degaussing better than wiping?

Only if you never want to reuse the drive. Wiping with verification leaves the drive usable and resellable. Degaussing leaves it worthless. If recovery value matters, wipe. If policy forbids reuse, degauss or shred.

How much does a degausser cost, and should we buy one?

Degaussers are capital equipment that needs periodic checks of field strength, and they only handle magnetic media, so you still need another method for SSDs. For most companies, paying per drive for onsite or offsite degaussing works out simpler than owning a machine. Buying tends to make sense for organisations that degauss drives in volume, all year round.

Is a degaussed hard drive still e-waste?

Yes. It still contains aluminium, steel, circuit boards and rare-earth magnets. It should go to an authorised e-waste recycler, with the destruction recorded on your certificate.

Do you offer onsite degaussing?

Yes. PrivAce offers onsite and offsite hard disk degaussing across India, with free pickup in Mumbai, Navi Mumbai, Thane and Pune, with serials recorded before degaussing when your audit needs them, and a Certificate of Destruction afterwards.