A prediction market app lets people trade contracts on real-world outcomes — an election, a game, a data print — and the price of each contract moves with demand the same way a stock price does. That price is built to be read as a probability: a contract trading at 64 cents implies the market currently prices roughly a 64% chance the event resolves yes, because 64 cents is the level at which buying and selling that outcome are equally attractive. The order book is what does the converting, nudging the price toward whatever number leaves buyers and sellers indifferent at that level.
How a "yes" becomes a price
Most prediction markets are built on a simple contract structure: a "yes" share pays out $1 if the event happens and $0 if it doesn't, and a "no" share pays the opposite. Because the two outcomes are exhaustive — exactly one of them happens — a yes share and a no share on the same event have to be worth about $1 combined whenever the market has enough liquidity to enforce it. If yes is trading at 64 cents, no should trade close to 36 cents.
That $1 ceiling is what turns a price into odds. A share that costs 64 cents and pays out $1 or $0 is priced exactly the way an insurer prices a policy or a bookmaker prices a line: back out the price the risk was sold at, and you've backed out the probability the seller was implicitly assigning to it. The market doesn't need every trader to agree on that number — it only needs enough of them trading against each other that the price settles somewhere both sides can live with.
Reading the order book
Under the price is an order book, the same structure that prices stocks, perpetual futures, or spot crypto. Bids are the prices buyers are currently willing to pay for "yes"; asks are the prices sellers want to sell it at. The gap between the best bid and the best ask is the spread, and the size sitting behind each price level is the depth.
- Tight spread, deep book. The current price is well-supported — it would take a large order to move it meaningfully, so the probability it implies is relatively stable.
- Wide spread, thin book. A modest order can shift the price more than the underlying news would justify. Treat the displayed probability as noisier in this case, not as more precise just because it's a number.
- Order flow. A run of buys lifting the ask, level after level, is the book's way of saying new information (or new capital) is pushing the implied probability up in real time — often before a headline explains why.
Why price behaves like probability
The mechanism that keeps a prediction market's price honest is arbitrage, not consensus. If yes and no together cost more than $1, a trader can sell both and lock in the difference regardless of the outcome; if they cost less than $1, a trader can buy both and do the same. Both trades push the combined price back toward $1, which is what keeps a single contract's price interpretable as "the probability, as priced by whoever is willing to put capital behind a view right now."
A prediction market price isn't a poll of what people believe. It's a record of what people were willing to pay to be right.
That distinction matters for how much weight to put on the number. A price reflects the traders active in that specific market at that specific size — not a scientific sample of public opinion, and not the "true" probability in any deeper sense. Markets with more participants and more capital tend to track outcomes well precisely because it's expensive to hold a mispriced position against a determined opposing trader; thin or novelty markets don't have that discipline yet, and their prices should be read more loosely.
What moves the price
Three things push a contract's price, and it helps to tell them apart:
- New information. A poll, an earnings print, an injury report — anything that changes the odds of the underlying event moves traders to buy or sell, and the price follows.
- Order size relative to depth. A large order in a thin book can move the price without any new information at all. This is the case worth being skeptical of: a sudden jump is not always a sudden insight.
- Time to resolution. As an event's outcome becomes more certain — a game enters its final minutes, a vote count comes in — prices for genuinely likely outcomes drift toward $1 and unlikely ones toward $0. That convergence is mechanical, not a change in anyone's opinion.
Where Swop fits
Swop's trading agent works across spot, perpetual futures, and prediction markets from inside the same wallet — reading a market's depth and recent flow, summarizing it in a paragraph instead of a dashboard, and proposing a trade you approve before anything signs. That confirmation model is the same one Swop uses everywhere it touches your funds: the agent proposes, you approve, and nothing signs without a tap.
Swop is fully self-custodial — keys are generated and held on your device; Swop never holds them — and it runs on Solana, Ethereum, Base, and Polygon. Swop is available on iOS and Android, and as a web app at swopme.app.
FAQ
What is a prediction market app?
A prediction market app is a trading venue where the assets are contracts on real-world outcomes — will an event happen by a given date — instead of stocks or tokens. Each contract's price moves with trading demand, and that price is built to be read as a probability: a contract trading at 64 cents implies the market currently prices roughly a 64% chance the event resolves yes.
How does a prediction market's price become a probability?
Yes and no shares on the same event are built to settle at $1 and $0, so their prices have to sum to about $1 whenever the market is liquid. That constraint is what turns a price into a probability: if yes is worth 64 cents, no should be worth roughly 36 cents, because paying more than $1 for the pair, or less, creates a near risk-free trade that arbitrage quickly closes.
What's the difference between a market's price and the real probability?
The price is the market's current, collective estimate — not a guaranteed truth. It reflects whoever is trading, how much capital is behind each view, and how much liquidity sits in the order book. A thin market can be pushed by one large order; a thick one absorbs that same order with barely a flicker. Read the price as "the odds it currently costs money to disagree with," not as a verified fact.
How do I read a prediction market's order book?
The same way as any other market: bids are what buyers are offering, asks are what sellers want, and the gap between the best of each is the spread. A tight spread with size stacked on both sides means the current price is well-supported; a wide spread or thin depth means a modest order can move the probability more than the news alone would justify.
Does Swop have a prediction market?
Yes. Swop's trading agent works across spot, perpetual futures, and prediction markets from the same wallet, reading depth and flow and proposing trades you approve before anything signs. Swop is fully self-custodial — keys are generated and held on your device; Swop never holds them.
Written by the Swop product team. Editorial rules: a direct answer up front, no invented statistics, dates on everything, and links to primary sources.