Degaussing uses a strong magnetic field to remove data from magnetic storage devices. In addition to erasure, degaussing is generally a destructive technique in that it renders most magnetic media types unusable, with the exception of a few types of magnetic tape.  Degaussing is only effective on magnetic storage devices and is not suitable for any other technology, including solid state media, cell phones, and other similar storage devices.

While degaussing is an effective method of erasure, it should not be used as the sole method and should be followed by additional physical destruction. This is because it is impractical to verify that each individual hard disk drive or tape has been degaussed successfully.  However, degaussing before destruction provides the opportunity to use less stringent, less costly physical destruction procedures than would otherwise be necessary.

A limited number of modern HDDs will also contain small quantities of solid-state memory. This is sometimes referred to as ‘hybrid’ technology. Solid state memory will be unaffected by degaussing and may not be easy to detach for separate treatment. In an operational situation, it may not be easy to distinguish between HDD and hybrid devices so care should be taken to correctly identify media types prior to destruction.