True mirror online: how others see you

An ordinary mirror reverses left and right. The face you have seen every day of your life is that reversed face, and it is not the one anyone else sees. A true mirror, also called a non-reversing mirror, shows the face the right way round. Physical true mirrors use two mirrors at a right angle; online, the same thing is done by showing the camera without the mirror flip that phones add to the selfie preview.

The difference is only visible because no face is perfectly symmetric. A parting that sits on one side, a slightly higher brow, a crooked smile or a nose that leans a little all swap sides between the mirror and the true view. The face symmetry test measures how large those differences are, feature by feature.

Mostly familiarity. People tend to prefer what they have seen most often, and the face you have seen most often is your mirror image. Your friends have seen the other version, which is why a photo of you can look odd to you and normal to them. The unfamiliar version is not less attractive; it is just less familiar to you, and the strangeness fades after a few days of looking at it.

The TikTok inverted filter does the same flip on a video, and people are often surprised by it for the same reason. Neither view is the real one in any deeper sense: other people see the true view, and you are used to the mirror view.

• Live: open the camera and you see the true view first. Switch to the mirror view and back to see which features move.
• Photo: pick a photo and the tool levels your head, then shows it flipped and split down the middle of your face, each half doubled.
• Phone selfies: many phones save front-camera photos un-mirrored even though the preview was mirrored, which is why a selfie can look different from the screen a second earlier.
• Light: face a window and keep the phone at eye level; side light exaggerates the difference between the two halves.

Doubling each half of the face is an old way to make asymmetry visible: the left half mirrored makes one face, the right half mirrored makes another, and the two often look like relatives rather than the same person. That is normal. Every face has some asymmetry, and small differences are invisible in ordinary life. The research on facial attractiveness does find a preference for symmetry, but a modest one, and the doubled faces exaggerate the effect because the midline and the head angle are never perfect in a photo.

The bony asymmetry is structural and does not change with exercises. What changes how asymmetric a face reads is often simpler: a parting moved to the other side, brows groomed to the same height, and photo angle. If one side has always looked better to you in the mirror, it is probably the other side in the true view, which is worth knowing before choosing a parting or a photo angle.