SD Card Overwrite Protection Switch

Viewed from above, there is usually a switch on the right side of the SD card, which is the overwrite protection switch, while the MMC card does not. When the overwrite protection switch is turned off, the SD card will be overwritten and the data can only be read. When the overwrite protection switch is in the upper position, the data can be overwritten. Since this protection switch is optional, some brands of SD cards do not have this protection switch.

The principle of the overwrite protection switch is similar to the overwrite protection on cassette tapes, VHS video tapes, and computer disks. The closed state means overwritable, while the open state means protected.

If the switch is broken, the card can only become a write-protected read-only memory card. One way to get around this is to tape the notch so that the card will always be writable.