High-yield savings vs money market account: the real differences

Three products with similar names

A high-yield savings account and a money market deposit account (MMDA) are both bank deposit accounts. The FDIC's guide to insured deposits lists checking, savings and money market deposit accounts among the deposits it covers, within the standard limit per depositor, per bank, per ownership category. A money market mutual fund is something else: it is an investment fund, often offered by brokerages. The FDIC lists mutual funds among the products it does not insure and says deposit insurance does not cover investments even if they were purchased at an insured bank.

So the first question is not which earns more but which product you are looking at. If the account page says Member FDIC and calls it a money market account, it is a deposit. If it is a fund with a prospectus and a ticker symbol, it is an investment, and the comparison in this guide does not apply.

Two banks' terms side by side

The figures below come from the banks' own pages on October 29, 2026. Rates are variable and can change after you open the account. Capital One's 360 Performance Savings page did not display a readable rate when we checked, so we do not quote one; check the page yourself.

The Ally pair is useful because the rates match. When a bank pays the same APY on both, the money market account's checks and debit card cost nothing in interest, and the remaining question is whether you want that access attached to your savings. Some savers deliberately choose the account without a card so the money is harder to spend.

Worked example: when a tiered rate matters

The rates in this example are invented to show the math, not current market rates. A saver compares a savings account paying a flat 3.00% APY with a money market account paying 2.50% below $25,000 and 3.25% at $25,000 or more, where the tier is set by the whole balance, as in Ally's description of end-of-day balance tiers. Interest is estimated as balance x APY for one year with no deposits or withdrawals.

At $10,000 the savings account earns $300 and the money market account $250. At $24,999 the gap is still against the money market account: $749.97 versus $624.98. At $25,000 the money market account jumps to $812.50 against $750. The break-even is simply the tier threshold: below $25,000 the flat account wins, at or above it the tiered account wins by 0.25 percentage points.

Now suppose the balance hovers near the threshold. If it sits at $26,000 most of the year but drops to $23,000 for two months to pay a bill, the money market account earns the lower rate on those days and the advantage shrinks. A tiered rate only helps if your balance stays above the tier with a margin; if you regularly dip below it, the flat account is the simpler choice.

Questions to answer from the account disclosure

Tier rules differ by bank, so read the rate disclosure rather than the headline. These questions decide which account earns more for you and how easy the money is to reach.

• Does the tier rate apply to the whole balance, or only to the portion of the balance inside each tier? The worked example above assumes the whole balance.
• Is there a minimum opening deposit, a minimum balance to earn the APY, or a monthly fee below a balance? Any of these can erase a small rate difference.
• How many withdrawals per statement cycle are allowed, and what happens if you exceed it? Ally lists no fee but says it may close the account.
• Does the account come with checks or a debit card, and do you want that access on your savings?
• Are ATM fees at other operators reimbursed, and up to how much?
• Is the bank FDIC-insured, and does this deposit push your total at that bank above the coverage limit for your ownership category?

Who should pick which

Choose a high-yield savings account if the money is an emergency fund or a goal you transfer to checking a few times a year, and you prefer a little friction before spending it. Choose a money market account if you write occasional large checks from savings, such as a quarterly tax payment or a contractor deposit, and the bank pays at least the same rate at your balance. Skip both and look at Treasury bills or CDs only for money with a known date you will not touch; our Treasury bill guide covers that trade-off. Skip a money market fund if you need deposit insurance specifically.