Core concepts

Prices & order book

Outcome prices are probabilities expressed in USDC. This page covers the 0–1 price range, the order book, order types and lifecycle, and how the matching engine's price-time priority produces every fill. Payouts and the position view live on the Positions & payouts page.

The 0-to-1 range

Every outcome's share trades between 0 and 1 USDC. The price equals the market's estimated probability that the outcome resolves true.

0.50 means the market believes the outcome has roughly a 50% chance of being correct.
Prices move with new information and with order flow.
On binary markets the two outcomes' prices add up to roughly 1.00, minus a small spread.

Reading the order book

The order book shows the best bids (people willing to buy) and asks (people willing to sell) with their sizes. The gap between the best bid and best ask is the spread.

Order book — sample snapshot

ASK0.641,200ASK0.63800BID0.61950BID0.602,100

Best bid 0.61, best ask 0.63, spread = 0.02. Marketable orders cross the spread; limit orders sit inside or outside it. The UI displays decimal probability (0.00–1.00); the API accepts and returns prices in basis points (0–10000). For example, 0.64 in the UI is 6400 BPS on the wire.

Order types

Type	Behavior	Filling style
Limit	Rests in the book at a specified price until filled, cancelled, or expired.	Partial fills allowed; remainder rests.
Marketable	Crosses the spread and executes immediately against existing liquidity.	Walks the book until filled or no liquidity.

Both order types are limit orders submitted at a fixed price. A marketable order is simply a limit order priced to cross the spread on arrival, so it executes immediately against existing liquidity. Time-in-force variants (FOK, IOC, GTC) are not available.

Order lifecycle

1
Draft
2
Submit
3
Validate
4
Match
5
Rest
6
Fill
7
Settle

Linear lifecycle — every order walks this path; the matcher handles partial fills by repeating step 4 against multiple counter-orders.

1
Draft
You assemble an order locally — side, price, size, time-in-force.
2
Submit
The order reaches the API. Authentication and balance checks happen first.
3
Validate
The engine confirms market state, KYC tier, daily limits, and risk rules.
4
Match
The order is queued for the async matcher (the pending state). The matcher picks it up in order and executes marketable portions against the best available counter-orders.
5
Rest
Any unfilled remainder sits in the book at your specified price.
6
Fill
Other traders cross your resting order; you receive shares; rebates apply if you were the maker.
7
Settle
At resolution, winning shares pay 1 USDC each; losing shares pay zero.

The CLOB in one paragraph

A central limit order book records every resting buy and sell order. When a new order arrives, the engine matches it against the best available counter-orders using price-time priority.

Price priority — better-priced orders trade first.
Time priority — when prices tie, earlier orders trade first.
All trades happen at a single matched price per fill, derived from the resting order.

Maker and taker

Every fill has a maker and a taker. Your role determines whether you pay a fee or receive a rebate. See the Fees page for exact rates.

Maker

Your order rested in the book and was matched by someone else's order. Makers receive a small rebate.

Taker

Your order crossed the spread and consumed existing liquidity. Takers pay the trading fee.

Don't confuse price with conviction

A price near 1.00 does not mean the outcome is certain — it means the market believes it is very likely. Surprises happen; size your positions accordingly.

Self-cross protection

Orders that would match your own resting orders are rejected to prevent wash trading. Cancel and resubmit if you intentionally want to flip your position.