Use an image editor and choose Flip Horizontal or Flip Vertical
In Photoshop, go to Image > Image Rotation > Flip Canvas Horizontal or Flip Canvas Vertical
In GIMP, go to Image > Transform > Flip Horizontally or Flip Vertically
In Paint, open the image and use the Rotate menu to flip it
In Preview on Mac, use the Markup tools or edit in another app with flip support
In mobile photo apps, look for Edit > Crop > Flip
In HTML/CSS, use transform: scaleX(-1) for horizontal flip or scaleY(-1) for vertical flip
In Python with Pillow, use ImageOps.mirror() for horizontal flip or ImageOps.flip() for vertical flip
In command-line tools like ImageMagick, use -flop for horizontal flip or -flip for vertical flip
Save the flipped image in the desired format after editing