magstripe

Magnetic stripe, or magstripe, is a storage medium embedded on plastic cards that holds data through the magnetization of tiny ferromagnetic particles within a thin stripe. The stripe is divided into typically three tracks, encoded according to standards such as ISO/IEC 7811. Track 1 is designed for alphanumeric data and is commonly used for cardholder names and account information. Track 2 is numeric-only and widely used for the primary account number, expiration date, service code, and discretionary data. Track 3 is optional and rarely used in modern systems.

Data on magstripes is read by a magnetic swipe reader that detects changes in magnetic flux as the card passes by the read head. Encoding is designed to be robust for a consumer-friendly swipe, but the data on the stripe is often not encrypted by default. The exact layout of data varies by issuer and application, with track 1 and track 2 carrying different but overlapping information. In payment cards, for example, Track 1 may carry more human-readable information, while Track 2 carries critical numeric data used by many automated systems.

Applications of magstripes include payment cards, hotel room keys, transit passes, and employee badges. The technology is valued for low cost and broad compatibility, but it has limitations. Stripes can be damaged by wear, exposure to strong magnetic fields, or heat, and the data can be skimmed or cloned if readers are compromised. As a result, many regions have shifted toward chip-based (EMV) and contactless technologies, though magstripes remain in use for backward compatibility.