Magnetic Secure Transmission
A technology that uses magnetic pulses generated by an electromagnet to recreate the data stored along the length of a magnetic strip.
It was developed for payments. A phone with MST can be held against a swipe-style magnetic credit card reader, with the MST component simulating the swipe of a physical credit card. To the magnetic sensor of the credit card reader, the magnetic fields generated by MST are identical to the fields it would sense from a credit card's strip as it is swiped through the reader.
In this way, MST enables your phone to replace plastic payment cards in your wallet, much like NFC. MST has the advantage of working with common magnetic stripe readers, instead of requiring an NFC or chip reader.
MST, like NFC, has a very short range of about three inches.
MST was developed by LoopPay, which was acquired by Samsung. Samsung now owns MST technology and has put it into its phones.
As banks and credit card companies migrate to more secure technologies such as EMV (chip cards) and NFC, magnetic stripe payment will be discouraged and phased out, making MST less relevant over time.