What exactly does a market maker do?

Simply put, a market maker is a securities firm that stands ready to buy or sell a particular stock at publicly quoted prices at any time^[1]. Imagine you want to sell an unpopular stock immediately, but no one is buying at the moment. A market maker steps in and says, 'I'll buy it at my quoted price.' It trades with you using its own capital, so you don't have to wait.

The core role of a market maker is to provide 'immediacy'^[3]—letting you execute instantly without waiting for a counterparty. In markets like Nasdaq, market makers are the 'liquidity providers.'

Think of a market maker like a 'stock supermarket.' The supermarket has products (stocks) on the shelves with marked buy and sell prices. You want to buy a bottle of water—you pay the listed price and take it, no need to wait for the manufacturer to deliver. The market maker is the supermarket owner: they stock up in advance (buy stocks with their own capital), put them on the shelf, and wait for you to buy. If you want to sell the water back, they buy it at the listed price. This way, you can trade anytime without hunting for another buyer or seller.

Market makers solve the 'hard-to-find counterparty' problem. For illiquid stocks, without a market maker, your order might sit for days without execution. Market makers use their own capital and inventory to ensure trades happen instantly. Of course, they're not charities—they earn through the bid-ask spread while bearing the risk of price fluctuations.

What's the difference between a market maker and exchange 'matching'?

Many people think exchanges just 'match' buyers and sellers, but on Nasdaq, it's different. Matching (order-driven) puts all investors' buy and sell orders together and matches them by price and time priority. In contrast, a market maker (quote-driven) posts its own bid and ask prices, and investors trade directly with the market maker without waiting for another retail order^[5].

For example: matching is like a dating site that helps you find a match; a market maker is like a matchmaking agency that already has a 'pool' of candidates ready—you come in and get introduced immediately. Nasdaq is a typical quote-driven market, while the NYSE is a hybrid model: it has both auction matching and designated market makers (DMMs) to maintain order^[7].

Specifically, in a matching model, your buy order enters the exchange's order book, and the system automatically looks for a matching sell order. If no one is selling, your order sits there waiting. In a market maker model, the market maker provides continuous bid and ask quotes, so your order executes directly with the market maker without waiting.

In short: Nasdaq's market makers are member firms that trade securities with their own capital at their displayed prices, and multiple market makers compete for the same stock^[5]; the NYSE primarily uses auction matching, supplemented by DMMs who maintain order and conduct openings and closings^[7]. We'll detail how many market makers compete for a typical US stock later in 'How many market makers does a US stock usually have?'

How do market makers make money?

Market makers earn the bid-ask spread^[4]. They simultaneously quote a bid price and an ask price. For example, for a stock, they might be willing to buy at $10.00 and sell at $10.05. If you're in a hurry to buy, you pay $10.05; if you're in a hurry to sell, you get $10.00. The $0.05 difference is the market maker's profit, compensating for the risk they take (e.g., a sudden price drop).

Additionally, market makers earn through payment for order flow (PFOF): brokers route retail orders to specific market makers, who pay the broker a fee^[10]. This is why many brokers offer 'zero commissions.' However, regulators require brokers to fulfill best execution obligations—they can't sacrifice your execution price just to get paid^[10].

Let's dive deeper into the spread. Suppose you're a market maker quoting a bid of $10.00 and an ask of $10.05. A retail investor wants to buy 100 shares—they pay you $10.05 × 100 = $1,005. Meanwhile, another retail investor wants to sell 100 shares—you pay them $10.00 × 100 = $1,000. You earn $5 from this round trip. If you do many such trades in a day, the profit adds up. Of course, if the stock suddenly drops to $9.00 and you still have inventory, you lose. So market makers earn the spread by taking risk.

We'll detail how PFOF works and regulatory concerns about conflicts of interest later in 'What is the relationship between market makers and payment for order flow (PFOF)?'

How are Nasdaq and NYSE market-making mechanisms different?

Nasdaq is a fully electronic market, with an average of over 20 market makers per stock competing^[6]. These market makers simultaneously post bid and ask quotes through Nasdaq's system, and investors automatically execute at the best quote. This competition narrows spreads, benefiting retail investors.

The NYSE uses a Designated Market Maker (DMM) system^[7]. Each stock has only one DMM, whose duties include not only providing liquidity but also conducting opening and closing auctions and maintaining fair and orderly trading during market volatility. The NYSE also has electronic matching, but during extreme volatility, when circuit breakers or individual stock halts are triggered by rules, the DMM uses its own capital and professional judgment to help maintain orderly trading and conducts the reopening after a halt—the DMM does not decide to halt trading on its own. This hybrid model combines the efficiency of matching with the stability of market makers.

Specifically, on Nasdaq, when you place a buy order for a stock, the system automatically compares all market makers' quotes and selects the best ask price for execution. With many market makers competing, spreads are often very small, like $0.01. On the NYSE, the DMM is obligated to maintain market order. During extreme volatility, when circuit breakers or individual stock halts are triggered by rules, the DMM uses capital and professional judgment to help keep trading orderly and conducts the reopening after a halt—not deciding to halt on its own.

In other words, Nasdaq relies on 'quantity wins'—multiple market makers compete, narrowing bid-ask spreads; the NYSE relies on 'dedicated responsibility'—a designated market maker maintains order during regular trading and critical moments (e.g., open, close, abnormal volatility). That's the core difference between the two systems.

Can market makers manipulate stock prices and harm retail investors?

Market makers are strictly regulated and cannot manipulate arbitrarily. FINRA rules require that market maker quotes be firm, two-sided (both bid and ask), and continuous^[8]. Regulations also prohibit 'stub quotes'—posting fake prices far from the market with no intention to trade^[9].

However, market makers do have an information advantage: they see order flow and know buying and selling pressure. But the law prohibits them from using this information for insider trading or front-running. Overall, market makers make markets more efficient, but retail investors should be aware that their counterparty may be a professional institution. Understanding how they operate helps you make more informed trading decisions.

FINRA Rule 6272 requires that market maker quotes be firm, two-sided, and continuous—meaning they must post both a bid and an ask simultaneously^[8]. This prevents market makers from posting only bids or only asks, or posting fake extreme prices. The SEC also explicitly prohibits 'stub quotes'—fake extreme quotes far from the market that are not intended for execution—and requires market makers to continuously provide meaningful quotes^[9].

Additionally, at the legal level, Section 3(a)(38) of the Securities Exchange Act of 1934 defines 'market maker' as a specialist permitted to act as a dealer, or a dealer who regularly posts two-sided quotes for a security in the ordinary course of business^[12]. This provides the legal basis for regulation.

How many market makers does a typical US stock have?

On Nasdaq, the average stock has over 20 market makers^[6]. Popular stocks typically have significantly more than the average, while small-cap stocks may have only a few. The more market makers, the more competition, and the narrower the bid-ask spread, which benefits investors.

On the NYSE, each stock has only one Designated Market Maker (DMM), but the DMM is often backed by a large investment bank or professional market-making firm, which also competes electronically with other market makers. So even with one DMM, actual liquidity comes from multiple sources.

Nasdaq is an electronic, multi-market-maker, quote-driven market: market makers are Nasdaq member firms that buy and sell securities with their own capital at displayed prices; multiple market makers compete for the same stock^[5]. Unlike the NYSE's floor-based 'auction matching,' Nasdaq's market center is fully computerized and screen-based, connecting over 250 competing market makers, with an average of over 20 market makers per Nasdaq stock continuously posting bid and ask quotes for automatic execution^[6].

What is the relationship between market makers and payment for order flow (PFOF)?

Payment for order flow (PFOF) is a fee that a market maker pays to a broker in exchange for routing retail orders to that market maker for execution^[10]. For example, zero-commission brokers like Robinhood route orders to market makers like Citadel Securities, which earn from the spread and share a portion with the broker.

PFOF raises conflict-of-interest concerns: brokers might route orders to market makers that don't offer the best price in order to collect more fees. Therefore, the SEC and FINRA require brokers to ensure 'best execution'—your execution price must not be worse than what's available elsewhere^[10]. Understanding PFOF helps you judge whether your broker is truly getting you the best price.

Regarding the mechanism and regulatory controversy of PFOF, the Congressional Research Service (CRS) provides a neutral explanation: brokers route customer orders to market makers and receive compensation, raising conflict-of-interest concerns^[11]. FINRA Regulatory Notice 21-23 reminds that regardless of whether such compensation is received, brokers must fulfill their best execution obligations^[10].