A server includes: a processor, a transmitter/receiver to communicate with a communication terminal and a plurality of other communication terminals, and a storage storing instructions. The processor executes the instructions to: select at least one first user among the plurality of other users based on a viewing state indicating extent of viewing of content by a user, which is stored in a storage of the communication terminal, and a plurality of other viewing states by each of a plurality of other users, each indicating extent of viewing of the content, which is stored in a storage of each of the plurality of other communication terminals; and control the transmitter/receiver of the server to output information indicating at least one first other viewing state corresponding to the selected at least one first user among the plurality of other viewing states.