What is a market maker in options?

What a market maker does all day

At any moment, a market maker is quoting bids and offers on thousands of options series: every strike and expiry of every underlying it covers. Those quotes are generated by models and updated many times a second as the underlying moves, implied volatility shifts and inventory changes.

When a customer buys a call, the market maker usually sells it. When a customer sells a put, the market maker usually buys it. The market maker does not have a view on direction and does not want one. Its business is providing liquidity, collecting the spread, and managing the risk of the positions that accumulate as a result.

Many exchanges designate particular firms as primary or lead market makers in specific products, with obligations to maintain quotes of certain sizes and widths for much of the trading day, in return for advantages such as fee rebates or priority in allocations.

How they manage risk

Every trade leaves the market maker with a set of Greeks. Selling a call leaves it short delta, short gamma and short vega. The first and most immediate step is delta hedging: buying enough of the underlying, or futures, to offset the directional exposure. That hedge has to be adjusted continuously as price moves.

Gamma and vega are harder to hedge with stock. A market maker reduces them by trading other options, adjusting its quotes to attract trades that offset its existing book, or laying the risk off with other dealers. If it is short too many calls, it may raise its call offers to discourage further buying and lower its call bids to attract sellers.

What remains after hedging is inventory risk: the exposure to large, sudden moves and volatility shifts that the hedges cannot fully cover. That residual risk is what the bid-ask spread compensates for.

How quotes are set

A market maker's quote starts from a theoretical value: a model price based on the underlying, time, rates and the firm's own view of implied volatility for that strike and expiry. The bid and ask are then placed around that value, with the width depending on how liquid the contract is, how volatile the underlying is, and how much risk the firm already carries in that part of its book.

Inventory moves the quote. A firm that is already short many calls at a strike will skew its prices to discourage more call buying and encourage selling, nudging both bid and ask higher. That is how market makers steer their books without refusing trades, and it is one reason the price of an option can shift even when the underlying and broad implied volatility are unchanged.

Where the orders come from

Retail options orders in the US are often routed by brokers to wholesale market makers, who pay the broker for the order flow and fill the order at or better than the displayed market. Institutional orders more often go to exchanges, where several market makers compete, or are negotiated as blocks.

Market makers value retail flow because it is, on average, less informed about short-term price moves than professional flow, which lowers their risk of being picked off. Flow from sophisticated institutions is quoted more cautiously.

None of this changes the basic structure: on most customer trades, a market maker is the counterparty, and it hedges.

Why market makers matter to price

The hedging is what turns options positioning into stock buying and selling. If market makers are net short gamma across a market, their hedges require them to buy as prices rise and sell as prices fall, which amplifies moves. If they are net long gamma, they sell rallies and buy dips, which damps them.

That is the foundation of every gamma exposure map. The map is an estimate of the hedging that market makers will be required to do at each price, built from open interest and an assumption about which side of each position they hold.

The assumption is the weak point. Market makers' actual positions are not public, and they can differ from the convention at specific strikes, especially where large institutional trades have left dealers long options that customers sold. That is why dealer positioning is always an estimate, not a reading.