Magnets erase your phone or cards easily
Smartphones use NAND flash storage, which is immune to magnetic fields. Magnetic stripe credit cards require roughly 4,000 gauss to erase, far beyond any consumer magnet. EMV chip cards are entirely unaffected by magnets.
What we know
This belief originates from the era of floppy disks and early hard drives, which used magnetic storage and could be erased by strong magnets. Modern smartphones and tablets use NAND flash (solid-state) memory, which stores data as electrical charges in transistors, not magnetic domains. No consumer or household magnet can affect NAND flash storage.
Traditional magnetic stripe credit cards do use a magnetic medium, but the high-coercivity (HiCo) magnetic stripe requires an approximately 4,000 gauss field to rewrite, which is far stronger than typical refrigerator magnets, phone cases with magnets, or even most MRI machines at distance. The scenario of a wallet magnet or clasped bag erasing a credit card is not supported by the physics of HiCo magnetic stripes.
EMV chip cards, which have replaced magnetic stripes as the primary transaction method in most countries, use integrated circuits that are completely unaffected by magnetic fields. Contactless NFC payment cards similarly use RFID technology immune to magnets. The main risk to modern payment cards from magnetic cases or wallet magnets is effectively zero for chip-based transactions.
Common claims
- A fridge magnet can erase your phone's memoryFalse. Smartphones use NAND flash storage, which is completely immune to magnetic fields.
- Magnetic phone cases will erase your credit cardVery unlikely. HiCo magnetic stripes require approximately 4,000 gauss to erase; most consumer magnets produce far less.
- EMV chip cards can be erased by magnetsFalse. EMV chips are integrated circuits with no magnetic storage element.