A trader stands outside of the New York Stock Exchange (NYSE) on July 25, 2017 in New York City. Getty Images

J.P. Morgan Chase sent online brokerage stocks into a frenzy on Tuesday, after CNBC reported that the Wall Street bank is about to introduce an app for free and discounted trades. But J.P. Morgan's isn't jumping into a market that's filled just with big publicly traded names like Charles Schwab, TD Ameritrade and E-Trade. Over the last several years, numerous start-ups have popped up, catering to younger investors who are much more comfortable buying stocks on their phone than they are setting up a meeting with a financial adviser or even creating portfolios from their desktop. Apps work well if you're just getting started and don't have a lot of money to invest — maybe just a few hundred bucks — or if you don't want to pay the fees it takes for a human to manage your money. These apps are legit, and they're catching the attention of the big banks who need to reach digital audiences. Here's an overview of some of the more popular options.

Wealthfront

What it does: When you set up your Wealthfront account, you'll answer several questions that help the company create a risk profile for you. Then, it creates a custom portfolio and makes recommendations on how and where you should invest your money. The company claims that its software — created by its research experts — can manage money and keep fees lower than services provided by humans. Fees: 0.25% of invested assets. Minimum investment: $500 Unique features: Wealthfront professes "passive investing" — parking your money in index funds and letting it sit — versus active investing that requires frequent trading. The company recommends investing for at least five years and says it uses a "diversified portfolio" of low-cost funds to invest your money. It even has a unique tool that can tell you if you have enough money saved up to quit your job and travel.

Betterment

What it does: Like other options, Betterment helps you manage your money and create savings accounts for retirement, mortgages, college savings, tax planning and investing. Instead of entirely relying on algorithms or the choices you make on a questionnaire, Betterment also lets you reach out to licensed financial experts with questions on your accounts. Fees: 0.25% of invested assets or 0.40% for a premium account with a minimum $100,000 balance. Minimum investment: $0 Unique features: Betterment is similar to Wealthfront but also includes access to human advisers if you want them, either through phone or via online chat. Customers with a premium account can also talk to certified financial planners for help with retirement, college savings and more.

Acorns

Acorns app Source: Acorns

What it does: Acorns puts your money into preconfigured portfolios that it says were created by Nobel Prize-winning economist Harry Markowitz. You can deposit as much as you like, but it also automatically saves your spare change — what it calls microinvesting — and then automatically buys securities once you have enough money. Fees: $1 per month for a standard microinvesting account. $2 per month includes support for retirement savings with a recommended IRA. $3 per month includes a checking account and automatic retirement savings. Minimum investment: $0 to open an account, but you need $5 to start investing. Unique features: You can deposit money directly into Acorns, but you can also automatically round up the money you spend on purchases and have the rest deposited into your account. If you spend $2.55 on a coffee every day, for example, you can have the 45 cents of change put right into your Acorns account. Also if you shop with Acorns partners enough, some of the money you spend with them will be returned to your account. If you buy from Apple, for example, 1.2% of your purchase goes into your Acorns account (after 120 days.)

Robinhood

What it does: Unlike many new tools, with Robinhood you're the investor. That means you need to do your own research before investing. The app provides information, like a news feed on the stocks you follow, which you can use as a guide. Fees: U.S. securities trades are free, but you'll pay regulatory trading activity fees (TAF) up to $5.95. Foreign securities cost $50 per trade. If you need broker assistance on the phone, you'll pay $10 per trade. Minimum investment: $0 minimum deposit. Unique features: Robinhood puts your investments in your hands, so you're the one creating a portfolio. You won't be getting software or human investment advice. Robinhood also includes options trading, so you can bet long on the companies you like or place shorts on the companies you want to bet against, and earlier this year the company introduced a tool for buying cryptocurrencies.

Stash

What it does: Stash offers 30 different investment "themes." If you want to invest in companies that are focused on the environment, you can do that, or you can chose to invest in the "budding legal marijuana industry." You pick your options in a quick starter questionnaire, providing your age, income, saving goals and indicating if you're a conservative, moderate or aggressive investor. In total, there are more than 170 ETFs and stocks to pick from. Fees: Stash charges $1 a month for unlimited trades until you have more than $5,000 in your account, after which you pay $0.25% in fees per year. Minimum investment: $5 Unique features: Stash has a fun approach to its investments that lets you invest in different industries based on your interests, including really unique options like only investing in "companies with a conscience" or those that focus on workplace equality.

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