The microSD card is the smallest consumer-focused flash memory card in use today. It’s a variation of the standard SD card (short for Secure Digital) and uses a similar set of electrical connections. That makes it possible to use microSD cards in standard SD card slots with the use of an adapter. MicroSD was introduced as a smaller alternative for portable electronics.
Due to the demand for ever-smaller portable electronics, by the early 2000s, the traditional SD card was proving too large for many kinds of devices, such as smartphones. In 2005, the microSD card debuted at about one sixth the size and half the thickness of the SD card. An SD card measures 32 by 24 by 2.1 mm, while the microSD card is 15 by 11 by 1 mm.
Despite the much smaller size, microSD cards have the same underlying architecture, including the same electrical pinout connections. Thus, instead of needing a new microSD card slot on computers, microSD cards can slip into adapters and use existing SD card slots.
Aside from size, the major difference between SD cards and their microSD siblings is capacity. While the newest SDUC “ultra capacity” cards can support up to 128 TB, the microSD format is limited to a maximum of 1 TB.
In addition, while most SD cards have write-protect tabs that allow you to lock them from being written to or erased, the microSD card does not have room for a physical write-protect tab and therefore can’t be locked.
As you might expect, the microSD card is used to hold large volumes of data in devices that benefit from its miniature design. Larger devices still rely on regular SD cards when practical because they support much larger capacities, but in particular, devices like smartphones, dash cams, and small cameras (like action cameras) rely on the microSD card for its tiny shape.
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