Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for monitoring of pet feeding. The methods, systems, and apparatus include actions of: obtaining a first reference image of a container corresponding to a full state of the container; obtaining a second reference image of the container corresponding to an empty state of the container; obtaining a sample image of the container; based on the first and second reference images, determining an amount of content in the container from the sample image; and based on the amount of the content being less than a reference amount, notifying a user that the amount of the content is getting low.