In this article, the authors make detailed comparisons of the most notable robo-advisors in the US — namely, Betterment, Wealthfront, and Schwab Intelligent Portfolios. Although they are quite similar, they have their own features. Betterment uses smart financial models, such as a downside-risk optimization model, to make sure that each of its four primary investing goals (retirement, safety net, general investing, and major purchase) is based on a different stock allocation path. Wealthfront is more like a technology company, making sophisticated financial advice and investment strategies available to every individual investor at low cost by combining financial theory and machine learning. Schwab, as a traditional financial services firm, uses more traditional investment strategies in asset allocation.