The chain is a map of the market's opinions
An option chain is every contract on one underlying laid out as a grid: strikes run down the rows, one block per expiry, with calls on one side and puts on the other. It looks dense because it is complete — but each cell is just the same few columns repeated.
Those columns are the whole vocabulary:
- Strike / expiry — which contract this cell is.
- Bid / ask — the two live prices: the bid is the highest price a buyer will pay (where you sell right now), the ask is the lowest price a seller will accept (where you buy right now). The spread between them is the cost of crossing to trade (see the bid-ask unit).
- Volume — contracts traded today.
- Open interest (OI) — contracts that exist and are still open, a stock that carries over between days.
- Implied volatility (IV) — the market's expected movement, backed out of the premium.
A worked example
GENCO trades at $100. One row of its chain, the $100 call expiring in a month:
| bid | ask | volume | open interest | IV |
|---|---|---|---|---|
| 3.10 | 3.30 | 4,200 | 18,000 | 24% |
Read it left to right. You could sell at 3.10 or buy at 3.30; the $0.20 spread is what crossing costs. 4,200 contracts traded today, and 18,000 sit open — this strike is liquid and well-populated, so fills are easier and quotes tighter. The 24% IV is the market's expected movement priced into this contract; compare it strike to strike and a skew appears — downside puts often carry higher IV than upside calls, the market paying up for protection. No single column is the story. The chain is the market's attention map, and reading it is reading where opinion has clustered.
See it in kestrel
The columns mean more when the underlying is a real, moving session. Run one and read the tape the chain would be quoted against:
npx kestrel.markets sim s-p-500-etf-pandemic-volatility-crashThat runs a deterministic simulation over a generic broad-ETF session — managed licensed data, no wall time, no signup, no card — and prints a certified proof URL. The Frame surfaces the same quote structure the chain is built from, so bid, ask, and volatility are values you can inspect rather than trust. Recompute the whole record on your own machine, byte for byte:
npx kestrel.markets certify https://kestrel.markets/proof/art_66d7dda7f0466f69c123463cKeep the chain one command away: drop the kestrel.markets MCP server into your client and the next session opens where this one left off — no account in between.