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Why do mirrors seem to flip left and right but not up and down?

 title: 'Mirror image - Wikipedia'

Mirrors do not actually flip left and right or up and down; instead, they reflect the third dimension, which is front to back[3][5]. When you look into a mirror, the light rays from your body are reversed along the axis perpendicular to the mirror surface[2][6].

To visualize this, imagine turning yourself 180 degrees to face your reflection[2]. Because you have rotated your body to match the reflection, your brain interprets the front-to-back reversal as a left-right swap[2]. This perception is simply a result of how we orient ourselves relative to the mirror[6].