Both. You can't have a measurable feature smaller than the Planck length, but that's not relevant to QR decoding in any practical sense. As for the practical l

Both. You can't have a measurable feature smaller than the Planck length, but that's not relevant to QR decoding in any practical sense. As for the practical limits, try using your phone to take a picture of something very far away, or very tiny, and see what happens.