Yes, you can place transfer stickers on windows. If your design is especially delicate, remove the paper backing and apply it to the window then let it sit for 24 hours before removing the transfer tape. This gives your sticker time to adhere more strongly to the surface and makes it easier to remove the tape while leaving the design intact.
It's important to note that we use a strong adhesive so they may take some effort to remove from a window. After removing your transfer sticker, if any residue is left it can be washed off with soap and water.