What is an online recommendation engine?

An online recommendation engine is software on a website or app that suggests products, content or offers to each visitor, based on their behavior, their preferences and what similar people chose.

An online recommendation engine suggests items to each visitor on a website or app: the products in a “customers also bought” row, a personalized homepage, the order of search results, the next video, or the products in an email. It works from what the visitor has browsed and bought, what they have told the site directly, the context they are in, and what similar visitors chose.

Recommendation engine, recommendation system and recommender system all mean the same thing. In 2026 the definition is widening to include AI assistants that write the recommendation itself, such as a meal plan with a shopping list or a full basket for a project.