People or objects are duplicating in generated images

Symptom

• You specify a single person or a single dog, but several people or objects appear.
• Only certain parts, like hands or faces, seem to multiply.

When it happens

• When generating with Stable Diffusion 1.5 at too high a resolution, such as 1024px or more.
• When generating at an extremely tall or wide resolution.

Cause

• SD1.5 was trained on square images around 512px, so its compositions tend to fall apart at larger resolutions.
  • For the background, see → Why generate at 512px × 512px?.

Solution

• Generate at a size close to the model's recommended resolution
  • For SD1.5, try around 512-768px.