A robo-advisor is an online service that builds and manages an investment portfolio for you automatically, run by software rather than a person picking stocks. You answer questions about your goals, timeline and tolerance for risk, and the service puts your money into a mix of low-cost funds, then rebalances it and handles certain tax moves on its own. The two largest independent US services, Betterment and Wealthfront, charge about 0.25% a year to manage the automated tier.

How a robo-advisor works

The model is deliberately simple. When you open an account, the service asks a short set of questions, typically about your age, when you expect to need the money, and how much of a drop you could stomach. From your answers it assigns a target mix of assets, usually spread across a handful of exchange-traded funds that track broad stock and bond markets. For the difference between the funds these services use and traditional mutual funds, see our explainer on ETFs versus mutual funds.

After that, the software does the work a human advisor would otherwise do by hand. It invests new deposits into the target mix, and when market moves push the portfolio away from that mix, it rebalances, selling what has grown too large and buying what has shrunk. Many services also offer tax-loss harvesting in taxable accounts, selling positions at a loss to offset gains elsewhere, which can trim a tax bill but matters far more to large taxable balances than to small or tax-sheltered ones. None of it requires you to choose individual investments.

Most robo-advisors will open the account types ordinary savers use: taxable brokerage accounts, and tax-advantaged retirement accounts such as traditional and Roth IRAs. The category grew up in the years after the 2008 financial crisis, when startups including Betterment and Wealthfront argued that the basic job of building and maintaining a diversified portfolio did not need an expensive human, and could be automated and sold cheaply. Large incumbents followed with their own versions, so the choice today runs from standalone apps to robo tiers bolted onto the big brokerages.

What it costs

The headline fee is low, but it is not the whole cost. Betterment's pricing page lists a base price of "$5/month" for its automated investing accounts, which drops to a 0.25% annual fee once you set up recurring monthly deposits of $200 or more, or reach a balance of $24,000 or more. It has no account minimum, and it reduces the rate to 0.15% on household balances above $1 million and 0.10% above $2 million. Its Premium tier, which adds access to human financial planners, costs 0.65% a year and requires $100,000. Wealthfront states on its own pricing page that its advisory fee for its portfolio is just 0.25% annually, and NerdWallet lists a $500 minimum to open its automated account.

On top of the advisory fee, you also pay the expense ratios of the underlying funds, which the service does not collect but which still come out of your returns. The other thing to watch is the flat-fee math. Betterment's $5 a month works out to $60 a year, which is a modest 0.25% on a $24,000 balance but a steep effective rate on a few thousand dollars, which is exactly why the service switches you to the percentage fee once your deposits or balance cross its thresholds.

What it does well, and where it falls short

The case for a robo-advisor is discipline at low cost. It builds a diversified portfolio, keeps it balanced, reinvests automatically and does not panic, which removes a lot of the behavior that hurts do-it-yourself investors. For someone who wants a hands-off, rules-based account and does not want to research funds, that is a genuine service for a small fee.

The limits show up as your life gets more complicated. A questionnaire-driven model does not handle the judgment calls a good human planner does: how to coordinate a pension, a business sale, stock compensation, or an inheritance. Access to a human is limited and usually costs more, as Betterment's 0.65% Premium tier shows. And the automated tax-loss harvesting that services market heavily is more valuable to larger taxable accounts than to small or tax-sheltered ones.

Robo-advisor, DIY index funds, or a human

Think of it as a middle option. Buying a couple of broad index funds yourself is cheaper still, because you skip the advisory fee entirely, but you have to rebalance and stay the course on your own. A human advisor costs more, often around 1% a year, but can handle complex planning a robot cannot. A robo-advisor sits in between: more automation than doing it yourself, less tailoring than a person. For the wider shift that produced these services, see our guide to what fintech is.

What to watch

Judge a robo-advisor on its all-in cost, not just the advisory fee: add the fund expense ratios to the management fee, and check whether a flat monthly charge or a percentage fee applies to your balance. Then ask whether your situation needs the judgment of a person, because that is the one thing the software is not built to provide. For many people starting out with a simple goal and a steady paycheck, that trade is a reasonable one: a low, automated fee in exchange for a diversified portfolio they do not have to tend. For someone with a tangled tax picture or a one-off event like a windfall or a business sale, the cheaper headline fee can end up costing more in missed planning than a human would have charged.