As part of the standard, cards have three protection methods: A TMP_WRITE_PROTECT bit, a PERM_WRITE_PROTECT bit, and a PWD register. The PERM_WRITE_PROTECT bit permanently write protects the card.

The write protection switch is a convenient failsafe to quickly prevent your camera from overwriting SD cards bearing your cherished photos.

Most SD cards are write protected, and even when you think write protection is disabled Windows still often won’t recognize the card as writeable.