US Patent 12117762 Attachment and image forming system

An attachment is used with an image forming apparatus. The image forming apparatus includes a main assembly including a photosensitive drum and a main assembly portion-to-be-engaged, and includes a developing unit including a developing container, a developing roller, and a mounting portion. The attachment includes a first engaging portion, and a second engaging portion. The attachment is mountable to the mounting portion in a state in which a toner container is not mounted to the mounting portion. The attachment does not include a toner accommodating portion for accommodating the toner.