What is triple witching (and quad witching)?

What expires

Every third Friday is a monthly options expiration. In the last month of each quarter, the quarterly stock index futures contracts expire too, including the widely traded S&P 500 and Nasdaq-100 futures, along with the options on those futures that share the date. Quarterly index options, which often carry the largest open interest of the year, expire alongside the regular monthlies.

Settlement timing matters. Index futures and the standard monthly SPX options settle to a special opening quotation on Friday morning, calculated from the opening prices of the component stocks. Single-stock and ETF options settle on the Friday close. So triple witching has two pressure points in the same day: the open, where index settlement is set, and the close, where equity options settle.

When the third Friday falls on an exchange holiday, expiration moves to the business day before it.

Why volume spikes

Several large flows land together. Traders holding expiring futures who want to keep their exposure roll into the next quarterly contract, though much of that rolling happens in the days before expiration rather than on the day itself. Holders of expiring options close, exercise or let them settle, and dealers unwind the hedges that were attached to them.

Index rebalancing often coincides. S&P Dow Jones Indices, for example, makes its quarterly index rebalances effective after the close on the third Friday of the quarter's final month, so index funds have to trade into the closing auction to match the new weights. That pushes a large share of the day's volume into the final auction.

The combination means closing auctions on triple witching days are often among the largest of the year. Large volume does not mean large price moves; much of it is offsetting.

What it does to the market structure

For dealer positioning, triple witching is the largest monthly OPEX of the quarter. Quarterly index options are where much institutional hedging sits, so a significant share of the board's gamma can expire at once. The structure that was damping or amplifying moves in the weeks before can look different the following Monday.

That is why traders often look at a gamma map with and without the expiring contracts in the days before. Levels that belong mostly to the quarterly expiry are levels that will not exist next week, and the regime at the current price can change once they are gone.

The weeks into triple witching also see the same vanna and charm currents discussed around any large expiration. With more open interest expiring, those currents can be larger, though they remain dependent on volatility and on the usual assumptions about which side dealers hold.

The days around it

Much of the futures activity happens before the day itself. Traders holding the expiring quarterly contract usually roll into the next one over the preceding week or so, and the roll shows up as heavy calendar-spread volume in futures rather than as directional trading. By the Friday, much of the futures open interest has already moved to the next contract.

Options open interest, by contrast, tends to stay in place until the end. Dealers carry the hedges for those positions right up to settlement, and the hedges come off either at the morning settlement for index products or at the close for equity options. That is why the structure on the gamma map can stay intact through Thursday and then change abruptly over the weekend.

What it is not

Triple witching is not a reliable directional event. There is no rule that markets rise or fall on the day or the week after. Commentary about witching-day volatility is mostly about volume and about the price action around the open and close settlement prints.

It is also not the same as the quarter-end date on which some large structured hedges reset. Those typically roll on the last business day of the quarter, which falls one to two weeks after triple witching. The two dates are often confused.

And it is not unique to US markets. Many exchanges worldwide schedule quarterly derivatives expiries on similar Fridays, and some have their own names for the day. The mechanics, overlapping expiries and settlement prints, are broadly similar.