The answer to 'why is my window pet stains' is that pet stains on windows are typically caused by your pet rubbing against the glass or leaving nose or paw prints. This can happen if your pet is trying to look outside or scratch at the window. The stains are usually a combination of dirt, oils, and saliva from your pet's interactions with the glass.
To clean pet stains from windows, first try a mild soap and water solution or a dedicated window cleaner. Gently wipe the stained areas and be sure to dry the windows completely. For tougher stains, you may need to use a glass cleaner with ammonia or vinegar. Always test a small, inconspicuous area first. If the stains persist, you may need to call in a professional window cleaning service to fully restore your windows.