What is actually being compared
An option is uniquely defined by three things: the underlying coin, the strike and the expiry. If two venues list a contract with the same three, it is the same instrument, and the price difference is the opportunity.
The difficulty is that venues describe it four different ways and quote it in different currencies. Deribit and OKX price the premium in the coin itself, Bybit and Binance in dollars. Converting between them by index is correct: the dollar payout at expiry is identical. But the settlement and margin currencies differ, and hedging such a position is harder than it looks.
Why dollars, not percent
Percentages mislead on options. A contract costs twenty-five dollars and the gap is eight: that reads as "thirty-five percent", yet it is one tick. Conversely a deep in-the-money option shows half a percent, which is a thousand dollars per contract.
So the scanner sorts by money, with the percentage beside it for scale rather than as the headline.
Tick size is a trap of its own
Coin-quoted venues use a minimum increment of 0.0001 of the coin. For bitcoin that is around eight dollars. On a hundred-dollar option that tick is eight percent of its price — and a "gap" of that size between venues means rounding, not opportunity.
Hence the tick column: if the edge is close to it, you are looking at a price grid rather than a market. Rows where the edge is below the tick are filtered out, but the figure is shown — the judgement should stay yours.
Junk quotes
Options books are thin, and some instruments carry orders like "bid ten" when the real price is four thousand three hundred. That produces spreads of thousands of percent and looks like the find of the century.
The defence is simple: every quote is checked against the median across the other venues and anything far from it is discarded. Without that filter the top of the list would consist entirely of such artefacts.
What the scanner does not do
- No fees: on options they are usually charged on the underlying's value rather than the premium, and depend on account tier.
- No depth: the best order may be for a single contract.
- No reconciling of settlement currencies: the payout matches, the margin does not.