Canon EOS 6D Mark II Instruction Manual page 72

3 Formatting the Card
If you format an SDXC card with this camera and then insert it into
another camera, an error may be displayed and the card may become
unusable. Certain computer operating systems or card readers may not
recognize a card formatted in exFAT.
When the card is formatted or data is erased, only the file management
information is changed. The actual data is not completely erased. Be
aware of this when selling or discarding the card. When discarding the
card, perform low-level formatting or destroy the card physically to
prevent personal data from being leaked.
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