Secure Digital Card (SD Card)

Last Updated: January 21, 2013

Definition - What does Secure Digital Card (SD Card) mean?

A Secure Digital card (SD card) is a non-volatile form of flash memory for portable and mobile devices. Because it is not proprietary, SD card usage is widespread. SD cards are located in thousands of consumer electronic device models, including mobile phones, digital cameras, camcorders, tablets and portable audio players.

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Techopedia explains Secure Digital Card (SD Card)

SD cards come in three compatible sizes, as follows:

MicroSD (15 mm × 11 mm)
MiniSD (21.5 mm × 20 mm)
SD (32 mm × 24 mm)

SD cards provide large-capacity storage in a tiny package with very low power draw, which is crucial because SD cards are often used in battery powered devices. SD cards also provide a broad range of storage capacity - from a paltry 16 MB at inception to the current maximum of approximately 32 GB. However, the next generation of SD cards, known as SD eXtended Capacity (SDXC), holds up to 2 TB (2000 GB) of data. SD data transfer speeds range from 2 MBps to approximately 90 MBps. By default, SD cards use the File Allocation Table (FAT) family of file systems (FAT16, FAT32, exFAT).

A key SD card feature is that it may be transferred between compatible devices. For example, vacation photos may be transferred from a digital camera to a PC. After inserting the camera's micro-SD card into the PC's corresponding slot or adapter, the PC recognizes the card as a new drive.

The SD format is governed by the SD Association - a global consortium of manufacturers.