Prediction Market Glossary: 100 Terms Explained

TL;DR

• Resolution is how a market settles: the written rules and named source that decide which outcome happened, so winning contracts can pay $1 and losing ones pay $0.
• A market maker is a trader or algorithm that posts both buy and sell prices on a contract, giving everyone else someone to trade against.
• Price and probability are the same number: a contract at $0.63 implies a 63% chance. Volume (activity) and open interest (money still at stake) are different numbers and often get confused.
• The same event can price differently on Polymarket, Kalshi, Limitless, Predict.Fun, and Opinion, which is why cross-platform comparison and normalization matter.

Ever opened a prediction market and run into "resolution source," "open interest," or "oracle" and quietly closed the tab? You're not alone, because most of this vocabulary doesn't come from betting or investing in any intuitive way.

Resolution is how a market settles: it's the process of determining which outcome actually happened and paying out the contracts that predicted it correctly. A market maker is a trader or algorithm that posts both buy and sell prices on a contract, giving other traders someone to trade against. Below are 100 terms you need to read odds, compare contracts, and understand how markets on Polymarket, Kalshi, Limitless, Predict.Fun, and Opinion actually work.

The glossary is grouped into eight sections, so you can read it top to bottom or jump to the term you just hit in a market description.

What Are the Core Mechanics Terms Every Trader Should Know?

What Is a Prediction Market?

A prediction market is a platform where people trade contracts tied to the outcome of a future event, and the trading price reflects the crowd's estimated chance that the event happens. It works like a stock market for outcomes instead of companies. For the full primer, see our guide to prediction markets.

What Is a Contract?

A contract is the tradable unit in a prediction market. Each one represents a specific outcome of a specific event, like "Yes, the Fed cuts rates in December."

A contract settles at $1 if the outcome happens and $0 if it doesn't. Everything in between is just the market's running estimate of which way it will go.

What Is an Event Contract?

Event contract is the regulatory term, used especially in CFTC filings, for what most people call a prediction market contract. It's a financial instrument whose payout depends on the outcome of a specific, verifiable event.

What Is a Share?

Share is the word many crypto-native platforms use for a single contract. Buying 100 Yes shares at $0.40 costs $40 and pays $100 if Yes wins. The terms "share" and "contract" mean the same thing in practice.

What Are Yes and No Contracts?

A Yes contract pays $1 if the event happens and $0 if it doesn't. A No contract does the opposite.

The two sides sum to roughly $1.00 before fees, since one of them has to be right. If Yes trades at $0.63, No should trade near $0.37.

What Is a Binary Market?

A binary market has exactly two possible outcomes, Yes or No. Most contracts are structured this way, even when the underlying event has more nuance. A binary market might ask "will candidate X win more than 270 electoral votes" instead of trying to predict an exact vote count.

What Is a Multi-Outcome Market?

A multi-outcome market has more than two possible outcomes, and each outcome gets its own contract. "Who will win the election" with five candidates listed is five separate binary contracts that should sum to roughly 100% combined.

When the total drifts above 100%, the extra is called the overround.

What Is a Scalar Market?

A scalar market resolves to a value within a range instead of a flat Yes or No, like "what will the unemployment rate be." The payout scales based on where the actual number lands.

Scalar markets are less common than binary ones, but they show up often in economic data markets.

What Is a Conditional Market?

A conditional market only becomes active, or only resolves meaningfully, if a prior event happens first. An example is "if Candidate X wins the primary, will they win the general election."

Conditional markets let you isolate a specific downstream question without betting on the entire chain of events.

What Is a Strike Price or Threshold?

A strike price, or threshold, is the specific number or condition a market is built around, like "will inflation exceed 3.5% in the next CPI report." Markets built on a threshold let you trade on a precise claim instead of a vague direction. Stacks of thresholds on one data release are common in CPI markets.

What Is Implied Probability?

Implied probability is what a contract's price says the market thinks will happen. A contract trading at $0.63 is a 63% implied probability, and one at 8 cents implies an 8% chance.

Price and probability are the same number on these platforms, just expressed differently. It's a starting point for reading sentiment, not a guarantee, and how well it holds up is covered in our piece on prediction market accuracy.

What Are Odds in a Prediction Market?

Odds are another way to express the same price. A $0.40 contract implies decimal odds of 2.5, because a winning $1 contract returns 2.5 times what you paid.

Traditional bettors often think in odds, while prediction market platforms usually display cents or percentages. The math converts cleanly in both directions.

What Is a Payout?

The payout is what a winning contract pays at settlement, which is $1 per contract. Your profit is the $1 payout minus what you paid and any fees.

A contract bought at $0.40 that wins pays a $0.60 gross profit per contract. One bought at $0.90 that wins pays only $0.10, which is why high-probability contracts have small upside.

What Is an Expiration Date?

The expiration date is the date a market stops accepting new trades and moves toward resolution. Some markets resolve immediately at expiration. Others have a short window afterward while the resolution source's data becomes available.

What Is a Market Category?

A category is the topic area a market falls under, like politics, economics, sports, weather, or crypto. Platforms group markets by category to make browsing easier, and some lean harder into certain categories than others. Opinion, for example, concentrates heavily on macroeconomic events like Fed decisions and inflation data.

What Is an Event Group?

An event group bundles related markets under one real-world event. A single Fed meeting, for instance, might hold separate contracts for a cut, a hold, and a hike.

Event groups make it easier to compare related outcomes side by side and to see how they add up.

What Do Resolution and Settlement Terms Mean?

What Is Resolution?

Resolution is the act of determining which outcome occurred and settling the market accordingly. Every market has resolution criteria written in advance, specifying exactly what evidence counts and which source decides.

Markets with vague resolution criteria are the ones most likely to end in disputes.

What Are Resolution Criteria?

Resolution criteria are the exact, pre-written rules a market uses to decide its outcome. They specify what counts as proof and what source is authoritative.

Reading them before trading is the single best habit for avoiding surprises, especially on markets covering fast-moving or ambiguous news. Our guide to reading market rules walks through what to look for.

What Is a Resolution Source?

A resolution source is the named authority or data feed a market uses to decide the outcome. It could be an official government report, a named news organization, or an on-chain oracle.

Always read it before taking a position. A market that resolves on "major news outlets reporting X" is riskier than one that resolves on a specific agency's published number.

What Is Settlement?

Settlement is what happens after resolution: contracts pay out and the market closes. It's typically automatic once resolution criteria are met, though some platforms have a dispute window first.

What Is Resolution Time?

Resolution time is the gap between the real-world event and the moment your payout arrives. It varies widely by platform, by market type, and by how clear the outcome is. The factors behind it are covered in our piece on resolution time.

What Is a Dispute Window?

A dispute window is a period after a market's proposed resolution during which traders can challenge the outcome before funds are finally settled.

Dispute windows are common on on-chain markets that rely on decentralized resolution, where a proposed outcome can be challenged before it's final. Centralized exchanges handle the same problem differently, with an internal review process, such as Kalshi's Outcome Review Committee, making the final call. Both approaches are ways of keeping resolution fair as the industry matures.

What Is an Oracle?

An oracle is a service that feeds real-world data onto a blockchain so an on-chain market can resolve based on verified information. Oracles are what let smart-contract markets settle without a single company deciding the outcome.

Polymarket resolves through UMA's optimistic oracle, while Opinion resolves each market against a defined data source using its own AI-assisted process.

What Is a Cancelled or Void Market?

A cancelled, or void, market is one where the underlying event can't be resolved as written, for example because a game is called off. What happens next differs by platform and is often defined in the market's own rules.

Kalshi may extend the expiration date and, failing that, settles using the last traded price or a committee ruling. Limitless refunds the original bet in some misresolved cases. Our guide to cancelled events covers the details.

What Is a 50/50 Resolution?

A 50/50 resolution is a fallback outcome in which each share redeems for $0.50 instead of $1 or $0. On Polymarket it's documented as a rare outcome that only appears after an escalating dispute process, not the normal result when an event fails to occur.

What Is Redemption?

Redemption is claiming your payout after a market resolves. On some on-chain platforms, winning positions are redeemed through the interface and converted back to your collateral asset, instead of appearing in your balance automatically. Check the platform's flow so you're not surprised by an extra step.

What Do Liquidity and Market Structure Terms Mean?

What Is a Market Maker?

A market maker is a trader or algorithm that continuously posts both a buy price and a sell price on a contract, providing the liquidity other traders transact against. Without market makers, a market can sit with no one willing to trade at any price.

Some platforms run their own automated market maker. On others, market making is done by individual traders and firms competing for the spread. Kalshi, for instance, runs an application-based market maker program.

What Is a Maker?

A maker is a trader whose order rests on the order book and adds liquidity, such as a limit order placed away from the current price. Makers are the ones other traders trade against.

Many platforms charge makers less than takers, and some, like Opinion, charge makers nothing.

What Is a Taker?

A taker is a trader whose order executes immediately against an existing order, removing liquidity from the book. A market order is the classic example.

Takers get speed and certainty of execution, and they typically pay the higher side of a platform's fee schedule in exchange.

What Is an Automated Market Maker (AMM)?

An automated market maker is a smart contract that sets prices algorithmically based on the ratio of contracts in a liquidity pool, instead of matching individual buy and sell orders. AMMs let a market function even when few human traders are actively quoting prices.

Most major platforms now run order books, though Limitless still prices some short-duration markets through an AMM. The tradeoffs are covered in our AMM vs. order book guide.

What Is a Liquidity Pool?

A liquidity pool is a stash of funds that an AMM uses to quote prices and fill trades. Liquidity providers deposit into the pool and share in the fees it earns, while taking on the risk that the pool's prices move against them.

What Is an Order Book?

An order book is the live list of buy and sell orders waiting to be matched at specific prices. A deep order book, meaning lots of orders stacked at prices close to the current price, makes it easier to enter or exit a position without moving the price much.

What Is a Central Limit Order Book (CLOB)?

A central limit order book is an order book that matches buyers and sellers by price and then by time, with the best prices filled first. It's the same structure traditional stock and futures exchanges use.

Kalshi, Polymarket, Predict.Fun, and Opinion all match trades through a CLOB, and Limitless uses one for most of its markets.

What Is a Bid?

The bid is the highest price a buyer is currently willing to pay for a contract. If you want to sell right now, the bid is roughly what you'll get.

What Is an Ask?

The ask, sometimes called the offer, is the lowest price a seller is currently willing to accept for a contract. If you want to buy right now, the ask is roughly what you'll pay.

What Is the Spread?

The spread is the gap between the best available buy price (the bid) and the best available sell price (the ask) on a contract. A tight spread, say a penny or two, signals a liquid, well-traded market.

A wide spread signals the opposite, and it means you'll pay more to enter and exit a position.

What Is the Midpoint?

The midpoint is the price halfway between the bid and the ask. It's often treated as the fairest single estimate of a contract's value.

Polymarket displays the midpoint as its headline price, and falls back to the last traded price when the spread is wider than $0.10.

What Is the Last Traded Price?

The last traded price is the price at which the most recent trade executed. Kalshi displays it as a contract's headline price.

In a thin market, the last traded price can be stale and sit well away from where you could trade right now, which is why the bid and ask matter too.

What Is Market Depth?

Market depth is how much size is resting in the order book at and near the current price. Deep books can absorb big orders without the price moving, while shallow books can't.

Two markets with the same spread can have very different depth, so it's worth looking past the top-of-book price.

What Is Liquidity?

Liquidity is how much capital is available to trade a given contract without moving its price significantly. A thinly traded market can move on a single large position, while a deeply liquid one absorbs large trades with barely a flicker.

Liquidity is the single biggest factor in whether a market's price reflects real consensus or just whoever traded last. See how the platforms stack up in our liquidity comparison.

What Is a Thin Market?

A thin market is one with little liquidity: few orders, wide spreads, and prices that can jump on a small trade. Thin markets aren't necessarily bad, but their prices deserve more skepticism than those of heavily traded markets.

What Is Slippage?

Slippage is the difference between the price you expected when placing an order and the price you actually got, caused by moving through multiple levels of the order book. It's usually small in liquid markets and can be significant in thin ones.

What Is Volume?

Volume is the total dollar amount traded in a market over a given period, usually quoted as 24-hour volume or as an all-time total. It measures trading activity, and it counts every trade, so the same position changing hands repeatedly keeps adding to it.

Volume and open interest can move independently of each other. Our guide to prediction market volume explains how to read both.

What Is Open Interest?

Open interest is the total value of all outstanding positions in a market that haven't yet been settled. It's a snapshot of what's at stake right now, not a running total.

Rising open interest alongside a stable price often means more traders are taking opposing views at the current level, not that the market has run out of opinions.

What Is a Maker Rebate or Liquidity Reward?

A maker rebate, or liquidity reward, is a payment platforms use to encourage traders to post resting orders. Polymarket's Maker Rebates Program shares part of taker fees with makers whose orders get filled, and Limitless pays daily rewards for orders placed close to the midpoint.

Kalshi runs its own incentive programs for liquidity providers. These programs are a big reason spreads stay tight on popular markets.

What Do Ordering and Trading Terms Mean?

What Is a Limit Order?

A limit order is an order to buy or sell a contract at a specific price or better. It won't execute until the market reaches your price, but it guarantees you won't pay more (or accept less) than you specified.

What Is a Market Order?

A market order is an order to buy or sell immediately at the best available price. Market orders execute fast but can suffer more slippage in a thin order book.

What Is a Fill?

A fill is the execution of all or part of your order. When only part of your order matches, it's a partial fill, and the rest keeps resting on the book until it's matched or you cancel it.

What Is a Position?

A position is the contracts a trader currently holds in a given market. A position can be closed before resolution by selling the contract back into the market.

What Is Cost Basis?

Cost basis is the average price you paid for the contracts in a position, including fees. It's the number you compare against the current price or the $1 payout to know whether you're ahead or behind. Cost basis also matters when it comes time to report taxes on prediction markets.

What Is an Early Exit?

An early exit means selling your contracts before the market resolves instead of waiting for settlement. You get the current bid price, which locks in a gain or loss now.

Early exits are possible whenever there's someone to buy from you, which is another reason liquidity matters.

What Is a Position Limit?

A position limit is a cap on how much exposure one trader can hold in a single market. On Kalshi, a position limit is defined as a dollar amount, the maximum loss a position can incur. Some contracts use a lighter position accountability level instead, which triggers reporting instead of a hard stop.

Limits vary by platform and contract. See our full breakdown of position limits.

What Is a Fee?

A fee is the cost a platform charges to trade or withdraw. Fee structures vary by platform and by transaction type (trading, withdrawal, currency conversion), and they matter most on smaller positions where a flat fee eats a larger share of the potential payout.

Several platforms use a trading fee that scales with price × (1 − price), which peaks at a 50-cent contract and shrinks toward the extremes. Our guide to prediction market fees compares the schedules.

What Is Collateral?

Collateral is the funds a trader puts up to take a position. On most platforms, collateral is locked for the life of the trade and returned, plus or minus the trade's outcome, at settlement or when the position is closed.

What Does Fully Collateralized Mean?

Fully collateralized means every contract is backed by the full $1 it could pay out, so there's no borrowing and no margin call. If you buy a Yes contract at $0.40, the other side has put up the remaining $0.60.

That structure caps your maximum loss at what you paid, which is a core difference from leveraged trading.

What Do Pricing, Strategy, and Risk Terms Mean?

What Is Price Discovery?

Price discovery is the process by which a market arrives at a price that reflects available information, through traders buying and selling based on what they know. It happens continuously, which is why prices move as news breaks instead of waiting for a scheduled update.

What Is Consensus Probability?

Consensus probability is the implied probability a market shows when you average pricing across multiple platforms. Looking at consensus instead of a single platform's number smooths out one exchange's quirks, like a thin order book or a regionally skewed trader base.

What Is Arbitrage?

Arbitrage is taking advantage of the same event being priced differently across platforms, by buying the cheaper side on one exchange and the equivalent on another. Opportunities tend to close quickly once enough traders act on them, which is part of why prices across platforms stay roughly aligned.

Fees, resolution differences, and capital lockup can erase an apparent gap. The practical side is covered in our guide to prediction market arbitrage.

What Is Overround?

Overround, also called the vig or juice in betting, is the amount by which the prices of all outcomes in a market sum to more than 100%. It represents the built-in cost of trading and shows up as extra probability across the outcomes.

Prediction markets generally carry a smaller overround than sportsbooks. See our breakdown of overround.

What Is Favorite-Longshot Bias?

Favorite-longshot bias is the tendency for longshots to be priced higher than their true chance and favorites to be priced lower. Traders overpay for a cheap shot at a big payout, and that shows up in the data across many kinds of markets. Learn more in our guide to favorite-longshot bias.

What Is Edge?

Edge is the gap between your estimate of an outcome's true probability and the probability implied by the price. If you think an event is 60% likely and the contract trades at $0.50, you believe you have a 10-point edge.

Edge is only real if your estimate is better than the market's, which is a high bar.

What Is Expected Value?

Expected value is the average result of a bet if you could repeat it many times. For a contract, it's your estimated probability times the $1 payout, minus the price you paid and fees.

A positive expected value means a bet is favorable on average, but any single outcome can still go against you.

What Is Hedging?

Hedging is taking a position that offsets the risk of another exposure, so a bad outcome in one place is cushioned by a good one in another. Prediction markets work well for this because contracts settle on a named event instead of a proxy. See our guide to hedging with prediction markets.

What Is Basis Risk?

Basis risk is the gap between what you're actually trying to protect against and what a financial instrument covers. A Bitcoin put option protects against price drops, not against a specific regulatory announcement.

Prediction markets reduce basis risk because they settle directly on the named event instead of a proxy for it.

What Is Calibration?

Calibration is how closely a market's stated probabilities match real-world frequencies. If events priced at 70% happen about 70% of the time, the market is well calibrated.

Calibration is the main yardstick researchers use to judge whether prediction markets are accurate.

What Is a Brier Score?

A Brier score is a number that measures how accurate a set of probability forecasts was, based on the squared gap between each forecast and what actually happened. Lower is better, and a score of 0 would mean every forecast was perfect.

It's commonly used to compare markets, forecasters, and models on the same footing.

What Is the Wisdom of the Crowds?

The wisdom of the crowds is the idea that the combined judgment of many people with diverse information tends to beat most individual experts. It's the theory behind why prediction market prices work as forecasts.

It works best when traders are independent, incentivized to be right, and trading in a market with enough liquidity to reflect them.

What Is a Whale?

A whale is a trader with a position large enough to move a market's price on their own. Whales can add useful information and liquidity, but in thin markets a single large order can distort the displayed odds. Our guide to prediction market whales covers how to read them.

What Is Wash Trading?

Wash trading is trading with yourself, or with a coordinated counterparty, to inflate volume without taking real risk. It can make a market look more active than it is.

Platforms and researchers are actively building tools to detect it. Our overview of wash trading explains the warning signs.

What Is Market Manipulation?

Market manipulation is any attempt to move a price to something other than the market's honest estimate, usually to profit elsewhere or to influence perception. Thin markets are easier to push around than deep ones.

Checking liquidity, depth, and the number of distinct traders helps. See how to spot a manipulated market.

What Is Insider Trading in Prediction Markets?

Insider trading in a prediction market means trading on material information that isn't public and that you have access to because of your role. Rules and regulatory guidance on this are still maturing, and the specifics differ by platform and jurisdiction.

Exchanges generally prohibit it in their rulebooks, and surveillance and enforcement are an active area of development as the industry grows.

What Are Correlated Markets?

Correlated markets are separate contracts whose outcomes tend to move together, like a party winning a state and winning the presidency. Their prices should stay consistent with each other, and gaps between them are a common source of both information and trading ideas. See our overview of correlated markets.

What Is an Opening Price?

The opening price is where a market starts trading when it first launches, before the crowd has had time to correct it. It often reflects the market creator's seed price or the first few trades.

Early prices tend to be noisier than later ones. Learn more about the opening price.

What Do Regulatory and Platform Terms Mean?

What Is the CFTC?

The CFTC, or Commodity Futures Trading Commission, is the US federal regulator for futures, swaps, and derivatives markets, including event contracts listed on regulated exchanges. A CFTC-regulated exchange, like Kalshi, operates under its oversight.

What Is a Designated Contract Market (DCM)?

A Designated Contract Market is the formal CFTC license that allows an exchange to list and trade contracts, including event contracts, under federal oversight. It's the specific regulatory status Kalshi holds.

Polymarket US is also a CFTC-regulated exchange, operated by QCX, which Polymarket acquired in 2025.

What Is Self-Certification?

Self-certification is the process by which a regulated exchange lists a new contract by certifying to the CFTC that it complies with the rules, instead of waiting for pre-approval. The CFTC can review the filing and step in if it has concerns.

Many event contracts have launched this way, and the filings are public.

What Is Preemption?

Preemption is the legal idea that federal law overrides conflicting state law. Kalshi's position is that federal oversight of its CFTC-regulated contracts preempts most state gaming restrictions, which is part of why it offers markets nationally.

That question is being actively litigated in several states, so treat it as a developing area. See our overview of prediction market regulation.

What Is a Clearinghouse?

A clearinghouse sits between the two sides of every trade on a regulated exchange and guarantees that both will be paid. It reduces the risk that a losing trader can't cover their side.

On regulated exchanges, this is a core part of how funds stay safe between trade and settlement.

What Is a Futures Commission Merchant (FCM)?

A futures commission merchant is a regulated broker that lets customers access a futures exchange. Some apps offer event contracts by routing orders through an FCM to a regulated exchange, instead of operating the exchange themselves.

What Is KYC (Know Your Customer)?

KYC is the identity verification process a platform requires before a user can deposit funds or trade. Requirements vary significantly by platform and jurisdiction.

Kalshi and Polymarket US require full verification, while Polymarket's international platform does not require government ID for basic wallet-connect access. See our guide to KYC requirements.

What Is a Jurisdictional Restriction?

A jurisdictional restriction is a limit on who can access a given market or platform based on where they're located, driven by local law. This is why availability differs by state or country, even on the same platform. Check access before funding an account. Our global regulation guide maps it out.

What Is Geoblocking?

Geoblocking is the technical enforcement of a jurisdictional restriction, usually by detecting your location from your IP address and blocking access. It's how platforms comply with local rules, and it's why a market you can see in one country may be unavailable in another.

What Do On-Chain and Crypto Terms Mean?

What Is an On-Chain Market?

An on-chain market is a prediction market where trades, collateral, and settlement are recorded on a public blockchain instead of a centralized company's internal ledger. Polymarket, Limitless, Predict.Fun, and Opinion all run this way, with Limitless on Base and Predict.Fun and Opinion on BNB Chain.

Positions and resolution data are independently verifiable by anyone.

What Is a Smart Contract?

A smart contract is code that lives on a blockchain and executes automatically when conditions are met. In prediction markets, smart contracts hold collateral, mint outcome tokens, and pay out winners according to the resolution.

What Is a Wallet?

A wallet is the software or hardware that holds your crypto keys and lets you sign transactions. On on-chain prediction markets, your wallet is how you connect, deposit, trade, and withdraw.

What Is Self-Custody?

Self-custody is holding your own funds and contracts directly, typically through a crypto wallet, instead of depositing them with a platform that holds them on your behalf. On-chain platforms generally let traders keep self-custody of positions until the trade is settled.

The tradeoffs between models are covered in our guide to custody.

What Is a Custodial Account?

A custodial account is one where the platform holds your funds on your behalf, as with a traditional brokerage. You log in with a username and password, and the platform handles the underlying assets.

This is how regulated exchanges like Kalshi work, and it's usually the simpler path for newer traders.

What Is a Stablecoin?

A stablecoin is a crypto token designed to hold a steady value, usually $1. On-chain prediction markets typically use dollar-pegged stablecoins like USDC as collateral, so a $1 payout means the same thing in crypto as it does in cash.

What Is a Gas Fee?

A gas fee is the network cost of processing a transaction on a blockchain. It's separate from the platform's own trading fee, and it varies by chain and by how congested the network is. Some platforms and wallets sponsor gas for users, which removes the cost.

What Is an Outcome Token?

An outcome token is a blockchain token that represents a position in one outcome of a market. Holding a Yes token means you hold a claim on $1 if Yes wins.

Because they're tokens, positions can in principle be moved between wallets, and they're visible on-chain.

What Is Yield on Collateral?

Yield on collateral is interest earned on the funds backing an open position while it waits to resolve. Predict.Fun routes collateral behind open positions into a lending market on BNB Chain so it earns yield, a mechanic none of the other four platforms offer.

It changes the math of holding long-dated positions, since idle capital isn't entirely idle.

What Is an On-Ramp?

An on-ramp is the path from regular money to crypto, such as buying USDC with a card or bank transfer. The matching term for going back out is an off-ramp.

On-chain platforms usually need you to get funds on-chain first, and the on-ramp you choose affects the cost and speed of getting started.

What Do Data and Aggregation Terms Mean?

What Is an Aggregator?

An aggregator is a service, like PredictionHero, that pulls prediction market data from multiple platforms into one view instead of requiring a user to check each exchange separately. An aggregator doesn't hold funds or execute trades. It's a read-only intelligence layer sitting on top of the actual exchanges.

What Is Cross-Platform Comparison?

Cross-platform comparison is checking the same event's pricing across multiple exchanges before acting on it. Polymarket, Kalshi, Limitless, Predict.Fun, and Opinion each attract different trader bases and operate under different rules, so the same event can carry meaningfully different implied probabilities depending on where you look.

This is the entire reason an aggregator is useful instead of bookmarking one platform. For the causes, see why odds disagree.

What Is Normalization?

Normalization is the process of adjusting prediction market data from different platforms into a comparable format, like converting different fee structures or contract sizes into the same implied-probability scale.

It's what makes a side-by-side comparison across five different platforms actually mean something, instead of comparing numbers that aren't measuring the same thing.

What Is Backtesting?

Backtesting is testing a trading idea against historical prices to see how it would have performed. It's a way to pressure-test a strategy before risking money.

Results depend heavily on the quality of the historical data and on assumptions about fees and fills. Our guide to backtesting a strategy walks through the process.

What Is an API?

An API, or application programming interface, is a way for software to request data or place orders on a platform directly instead of through a website. Traders and developers use APIs to pull prediction market data such as prices, order books, and history at scale.

Read-only data APIs are what make aggregation possible.

What Is Price History?

Price history is the record of how a contract's price has changed over time. It shows how the market reacted to news, how quickly information was absorbed, and how sure the crowd has been.

It's the raw material for charts, calibration studies, and backtests. Our guide to tracking prices covers the practical side.

What Is a Recurring Contract?

A recurring contract is a market that repeats on a schedule, like a daily or weekly question that resolves and then reopens with a new date. Examples include "Will the S&P 500 close higher today" or weekly data releases. Our overview of recurring contracts explains the pattern.

What Is a Short-Duration Market?

A short-duration market is one that resolves within hours or a day, like an hourly crypto price contract. These markets turn over quickly, which means faster feedback but also less time for information to build.

Limitless leans heavily into granular, short-duration markets.

Where Can You See These Terms in Action on Each Platform?

Each platform applies these mechanics a little differently, and knowing the vocabulary makes the differences easy to spot.

Polymarket is the largest crypto-native prediction market, with deep liquidity across most categories and a global user base. It also runs Polymarket US, a separate CFTC-regulated exchange that requires full identity verification. Read more in our guide to what Polymarket is.

Kalshi is the CFTC-regulated exchange, built as a Designated Contract Market and accessible to US retail traders without any crypto setup. It has led most volume trackers through much of 2026. Read more in our guide to what Kalshi is.

Limitless runs on-chain on Base with its own token. It mixes an order book with AMM-priced markets and leans into granular, short-duration contracts. Read more in our guide to what Limitless is.

Predict.Fun runs on BNB Chain and lets collateral in open positions earn yield while the trade sits unresolved, a mechanic none of the other four offer.

Opinion was built for macro traders first, with Fed decisions, CPI prints, and GDP data as its core categories, so its resolution sources tend to be government and central bank data releases. Read more in our guide to what Opinion is.

Want to see how these five compare on a single event? That's what PredictionHero's side-by-side view is built for.

Sources

• Polymarket Help Center. "Maker Rebates Program." help.polymarket.com
• Polymarket Help Center. "How Prices Are Calculated." help.polymarket.com
• Polymarket Documentation. "Resolution." docs.polymarket.com
• Kalshi Help Center. "How to Become a Market Maker on Kalshi." help.kalshi.com
• Kalshi. "Prices and Trades." news.kalshi.com
• Kalshi. "Designated Contract Market Rulebook." kalshi.com/regulatory/rulebook
• Limitless Documentation. "LP Rewards." docs.limitless.exchange
• Predict.Fun. "About." predict.fun
• Opinion Documentation. "Understanding the Order Book." docs.opinion.trade

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