noun
A person who uses a service, facility, or product. Often used in contexts like libraries, public transport, software, or commercial services.
図書館の利用者は毎年増えている。
The number of library users is increasing every year.
このアプリの利用者数は100万人を超
The number of users of this app has exceeded one million.
消費者 specifically means a consumer in an economic sense, someone who purchases and consumes goods. 利用者 can include non-paying users of a service.
Compound of 利用 (riyō, 'use, utilization') + 者 (sha, 'person'). The reading is standard on'yomi.