How to Flip an Image Horizontally or Vertically
Flipping and rotating get confused constantly, and they do different things. Rotating turns the picture while keeping everything the same way round. Flipping mirrors it, so left becomes right. The Image Editor does both.
When a horizontal flip is what you want
The commonest reason is a selfie. Front-facing cameras usually show you a mirror image while you frame the shot, then save the real one, so the photo you get is the opposite of the face you have been looking at all your life. Your own face looks subtly wrong to you and completely normal to everyone else. Flipping it horizontally gives you back the version you expect.
The other reason is composition. If a subject is looking out of the frame rather than into it, a horizontal flip fixes the direction without re-cropping. Designers do this constantly to make a photograph sit the right way in a layout.
What a flip always breaks
Any text in the picture becomes backwards. A sign, a book cover, a logo on a shirt, a number plate - all of it reads in reverse, and it is the first thing a viewer notices even if they cannot say what is wrong. So before flipping, look for lettering. If there is any, flipping is not available to you and you need to crop or rotate instead.
Faces are not perfectly symmetrical either, so a flipped portrait of someone familiar can look slightly odd to people who know them well. For a stranger's face, nobody can tell.
Vertical flips are rarer
A vertical flip turns the picture upside down while mirroring it, which is almost never what a photograph needs. Its real uses are technical - correcting a scan fed in the wrong way, or making a reflection effect under an image. If you simply want a photo the other way up, that is a 180 degree rotation, not a vertical flip.
Common questions
Does flipping lose any quality?
The flip itself is lossless - the same pixels in a different order. Re-saving a JPEG costs a little, so work from the original.
Is flipping the same as rotating 180 degrees?
No, and the difference is easy to see with any text. A 180 degree rotation leaves text upside down but still reading left to right. A vertical flip leaves it mirrored.
How do I know if my selfie needs flipping?
If you were holding the phone yourself with the front camera, it probably does. Look at any writing in the shot - if it reads backwards, the image is already mirrored.
Can I flip just part of an image?
Not in one step. You would crop the part you want, flip it, and place it back, which is a layered editing job rather than a single operation.
Will flipping remove the photo's metadata?
Not necessarily. If you want the camera and location data gone, remove it deliberately with the EXIF Data Viewer and Remover.
Need a picture the other way round?