Flip Images Horizontally, Vertically, and Create Mirror Effects in Photoshop
This tutorial shows two ways to flip images in Photoshop: flipping the entire canvas and creating a mirror effect with duplicated layers. You’ll learn where to access flip commands and how to combine a flipped layer with a mask to mirror only part of the image.

Step-by-step instructions
Open your image
Drag and drop your image into Photoshop.
Open Window → Layers to view layers if needed.
Flip the entire canvas
Go to Image → Image Rotation → Flip Canvas Horizontal to mirror left/right.
Alternatively, choose Image → Image Rotation → Flip Canvas Vertical to flip upside down.
Press Ctrl+Z (Windows) / Command+Z (Mac) to undo if needed.
Create a mirror effect on part of the image
Duplicate the image layer with Ctrl+J (Windows) / Command+J (Mac).
Select the top layer, then go to Edit → Transform → Flip Horizontal (or Flip Vertical).
Use the Rectangular Marquee Tool (M) to select the half you want to reveal (e.g., the left side).
Add a mask (Layer → Layer Mask → Reveal Selection or click Add Layer Mask in the Layers panel) so only the selected half of the flipped layer shows, creating a mirror look.