Ask most people how the biggest trading firms make money and you will hear some version of a familiar story: they are smarter than everyone else, they see the future, they place enormous bets and collect. It is a satisfying story. It is also, for a whole class of firms, almost entirely wrong. Firms like Jane Street, Citadel Securities, Susquehanna, and Optiver are not famous for calling the market. They are famous for being everywhere in it, all the time, on both sides of nearly every trade.
Understanding how market makers make money is one of the most clarifying things a serious individual investor can do. It pulls back the curtain on what markets have quietly become — fast, automated, and ruthlessly disciplined — and it offers a model of behavior that is far more useful to copy than any single trade idea. This is not a story about prediction. It is a story about process.
Strip away the technology and a market maker performs one ancient function: it stands ready to buy when you want to sell and to sell when you want to buy. In market language, it provides liquidity. Without someone willing to take the other side, your order to sell a stock or a futures contract would simply sit there until a natural buyer happened to show up. The market maker removes that wait.
It does this by continuously posting two prices for a given instrument: a bid, the price at which it is willing to buy, and an ask, the price at which it is willing to sell. The ask is always slightly higher than the bid. A firm might offer to buy a share at $49.98 and sell it at $50.02. That two-sided commitment — a live, executable quote on both sides of the market — is the core of the business. The firm is not expressing an opinion about whether the stock is going up. It is offering a service: immediacy.
The first and most important answer to how market makers make money is the bid-ask spread. In the example above, if the firm buys at $49.98 and almost immediately sells at $50.02, it captures four cents. That is the entire profit on that round trip. Four cents on a fifty-dollar share is a rounding error — and that is exactly the point.
The spread is tiny by design, but the business runs on volume. A modern market maker is not capturing four cents once. It is capturing fractions of a cent across millions upon millions of transactions a day, across thousands of instruments. The model only works if the edge is small, repeatable, and executed an enormous number of times. This is the same logic that powers a casino or an insurer: a modest, well-understood advantage applied relentlessly across a huge sample.
But spread capture is only the visible half. The harder half is inventory management. Every time a firm buys from a seller, it is now holding something it did not necessarily want to own. If the price drops before it can sell, that four-cent edge can be wiped out many times over. So the firm must constantly balance what it is holding — and, critically, it hedges. If it accumulates a position in one instrument, it may take an offsetting position in a closely related one — an index future, an ETF, an option — so that broad market moves cancel out and only the spread remains. The goal is to be paid for providing liquidity, not to be exposed to direction.
A market maker's profit is not a prediction that came true. It is a spread collected and a risk neutralized, thousands of times an hour.
What changed over the past two decades is not the function but the speed and breadth at which it runs. Quoting on both sides of a market used to be done by people on a trading floor. Today it is done by software measured in microseconds, and the firms that do it best are as much technology companies as financial ones. This is the same machinery we unpack in our piece on high-frequency trading explained — speed is a competitive necessity because the firm that can update its quotes fastest is the one least likely to be caught holding a stale price.
Electronic market makers also expanded far beyond single stocks. They became central to ETFs, where their ability to price a basket of underlying securities and keep the fund's price aligned with its true value is a core market function. They are dominant in options, where pricing requires constant, complex risk calculation. And as new venues appeared, they moved into crypto, applying the same two-sided, hedge-everything discipline to a far more volatile asset class. The instruments differ; the playbook does not.
One mechanism deserves a clear explanation because it is so often described in conspiratorial tones: payment for order flow. When you place a trade through a commission-free brokerage app, your order is frequently routed not to a public exchange but to a wholesale market maker, which pays the broker a small fee for the right to fill it.
Why would a firm pay for your order? Because retail orders, in aggregate, are valuable to interact with — they are generally smaller and less likely to be tied to information the firm needs to fear. The market maker fills your buy or sell, captures the spread, manages the resulting inventory, and shares a sliver of the economics with your broker. That arrangement is a large part of why you can trade without paying a commission. It is also genuinely debated: critics question whether you always get the best possible price, while supporters point to tighter spreads and free access. The honest framing is that the spread you do not see is the price of the commission you no longer pay.
Here is the part that matters most, and the part most retail commentary skips. These firms are not reckless gamblers who happen to have fast computers. They are, if anything, obsessive risk managers. Inventory risk — the danger of being stuck holding something when the market moves — is the thing that can end a market-making firm, and so it is monitored, hedged, and capped continuously. Position limits, automatic risk checks, and constant hedging are not afterthoughts; they are the business.
That is the lesson worth taking, and it connects directly to why firms like Jane Street and Citadel post record profits: durable profitability comes from controlling losses, not from being right about direction. The edge is small and known. The discipline around protecting it is enormous. Profit follows from the discipline, not the other way around.
The dominance of electronic market makers is the clearest single proof that markets are no longer human-paced. The prices you see, the speed at which your order fills, the tightness of the spread you trade against — all of it is set by algorithms running continuously, pricing risk and adjusting quotes faster than any person could. This is not a fringe development. It is the plumbing. When the firms that sit at the center of price formation are software-driven risk machines, the market itself has become algorithmic at its foundation. We explore the institutional side of this shift in why institutions use algorithmic trading.
The most important thing to understand is what your relationship to these firms actually is. You are not competing with a market maker, and you should never try to. You will not out-quote a firm that updates prices in microseconds, and you do not need to. They are providing the liquidity that lets your orders fill cleanly. In a real sense, they work for you every time you press buy.
What you can borrow is the mindset. The reason these firms endure is not secret speed — it is repeatable process and obsessive risk control. Define an edge you understand. Size your positions so a bad outcome cannot end you. Hedge or cut what threatens you. Execute the same way whether you feel confident or fearful. That is the discipline the new market makers pioneered and proved at industrial scale, and it is fully available to an individual willing to be systematic. You can read more about how we apply it at Algo Alpha.
The headline profits of these firms make for a dramatic story. The real story is quieter and more useful: markets reward whoever has the most disciplined process, not the boldest opinion. That is true at the scale of Jane Street, and it is true at the scale of a single retail account.
They earn the bid-ask spread — the small gap between the price they buy at and the price they sell at — and they capture it across a vast number of trades. Profit comes from repeating a tiny, well-understood edge millions of times while hedging away exposure to market direction, not from forecasting prices.
It is the difference between the highest price a market maker will pay to buy an instrument (the bid) and the lowest price at which it will sell (the ask). On a $50 stock the spread might be just a few cents. That gap is the market maker's compensation for standing ready to trade on both sides at any moment.
It is genuinely debated. Payment for order flow is a large reason brokerages can offer commission-free trading, and it is often paired with tight spreads. Critics question whether investors always receive the best available price. A fair summary is that the spread you do not see is the cost of the commission you no longer pay.
No. Market makers provide the liquidity that lets your orders fill quickly and cleanly — in effect they take the other side so you don't have to wait. You cannot and should not try to out-speed them. What you can adopt is their discipline: a defined edge, strict risk control, and consistent execution.
Because their core work — pricing risk, updating quotes, and hedging inventory — is done by software running in microseconds across thousands of instruments and many asset classes. The speed and automation required mean these firms compete on engineering as much as on finance, which is why markets today are algorithmic at their foundation.