What Is a Write-Protect Switch on an SD Memory Card?

by Ralph Horton

For several decades, photographers and video operators were limited by the capacity of their film. However, many 21st-century consumers prefer digital cameras and video recorders, which write data to high-capacity memory cards. The Secure Digital card is a standard among device manufacturers.


As digital cameras started appearing on the market, Panasonic, SanDisk and Toshiba united in January 2000 to form the SD Card Association. The organization developed, produced and promoted SD cards for use among manufacturers and consumers, and SD card technology gradually gained acceptance within the marketplace.


Several metal contacts are exposed on the back side of an SD card.

Full-size SD cards are universally rectangular in shape. When held facing the front side of an SD card, the top right corner appears tapered to allow for simple installation in consumer devices. SD cards measure 32 mm tall by 24 mm wide, or only slightly larger than the average postage stamp, and just 2.1 mm thick.

Lock Feature

The white write-protect switch can prevent users from erasing or writing to SD cards.

Most, but not all, SD cards have a small write-protection switch. This switch is visible along the top left edge of the card when held facing forward. If moved to the "Lock" position (down), this switch prevents any device from erasing or writing to the memory card. For example, if you place a locked SD card inside a digital camera, you are limited to merely viewing the images or video on the card. However, if the write-protect switch is in the unlock position (up), you can take new pictures, delete pictures, view your pictures and format the card.

About the Author

As a former public relations professional, Ralph Horton began writing in 2005. His work has been published in "The DELTASIG," a publication of the International Business Fraternity of Delta Sigma Pi. Horton specializes in writing for nonprofit organizations on topics ranging from sports to pharmaceuticals and wellness. He holds a Bachelor of Arts in communication from Miami University.

Photo Credits

  • photo_camera film can and sd card image by dwags from Fotolia.com