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Prediction Markets101

What is Polymarket? A complete beginner's guide

Polymarket is the world's largest decentralized prediction market, built on Polygon and settled in USDC. Here's how it actually works, what makes it different, and why it matters.

Prediction Markets 101 editorial team Updated April 16, 2026 11 min read

The one-sentence definition

Polymarket is an online marketplace where you bet on real-world outcomes by buying shares that pay one dollar if you're right and zero if you're wrong. The current price of a share is, by arbitrage, the market's probability that the outcome will happen.

If Polymarket is selling YES shares on "Will the Fed cut rates in March?" at 72 cents, the market thinks there is a 72% chance the Fed cuts. If it's selling NO at 28 cents (the complement, since the two must sum to $1), the same. A trader who thinks the true probability is 85% will buy YES at 72¢ because they expect the price to drift up toward 85 and, if correct, to settle at 100 at resolution. The cent differential is their edge.

That's prediction markets. The innovation Polymarket brings is making it work permissionlessly, globally, in dollars, without the custodial risk of betting companies or the regulatory overhang of centralized US exchanges.

What makes Polymarket different from a sportsbook

Traditional sportsbooks — DraftKings, FanDuel, Bovada — work like this: the house sets odds with a margin baked in (the "vig", typically 4–5%), you bet against the house, the house wins on average because the margin compounds over many trades, and you can't easily exit a position without placing a counter-bet at worse odds.

Polymarket works like this: there is no house. You trade against other users. Platform fees are transparently itemized on the trade ticket — Polymarket operated at 0% for years and introduced a fee schedule in late 2025, but costs remain materially lower than traditional sportsbook vig. You can exit any position at any time by selling back into the order book. The price of a share drifts with live sentiment, and whatever you pay is exactly the market's current probability estimate.

That's a fundamentally different financial product. A sportsbook bet is fixed-odds; a Polymarket position is a tradable security whose value fluctuates.

The mechanical differences

  • Fees. Sportsbooks bake 4–5% vig into every market. Polymarket added a per-trade fee schedule in late 2025 (previously 0%) — still materially less than sportsbook vig. Plus Polygon gas (a few cents) per transaction and onramp/offramp fees on fiat conversions.
  • Exit. Sportsbooks let you "cash out" at a margin-heavy price. Polymarket lets you sell your shares at the live market price, minus a few cents of spread.
  • Odds pricing. Sportsbooks express odds as +400 or -150. Polymarket expresses probability directly as a price between 0 and 100 cents. Traders coming from stocks find this more intuitive than American odds.
  • Custody. Sportsbooks hold your deposit. Polymarket holds your USDC in a smart contract wallet you control — you can withdraw anytime without manual review.

How a market works end-to-end

Here's what happens when you trade "Will Taylor Swift announce tour dates before July 1?" on Polymarket:

  1. The market is authored. Polymarket staff or a trusted author writes the question, resolution criteria (what specific event counts as YES), resolution date, and resolution source (where they'll look for the answer).
  2. Liquidity is seeded. The author or a market maker posts initial YES and NO orders to create a book. A fresh market with no liquidity can't be traded until orders exist.
  3. You place an order. You decide whether YES is underpriced. If you think there's a 65% chance Swift announces tour dates and YES is trading at 50 cents, you buy. Either:
    • Market order: Match the best existing sell order. Fills instantly.
    • Limit order: Post your own buy at 48 cents, wait for someone to take it. May never fill.
  4. Your position lives on-chain. You now own a YES share. You can see it in your Polymarket portfolio and, via your wallet, on Polygonscan. Polymarket's smart contracts are open-source.
  5. Market evolves. As news breaks (Swift's manager drops a hint on TV), the YES price moves. You can sell anytime at the current market price.
  6. Resolution. At resolution date, Polymarket's oracle (UMA's optimistic oracle) determines the outcome. If YES, YES shares pay out $1 each. NO shares become worthless.
  7. Payout. Your winning USDC appears in your wallet. You can withdraw to any Polygon-compatible wallet, bridge to Ethereum, or cash out to fiat via Onramper or Moonpay.

No human in this chain has discretion over your money. If Polymarket Inc. disappeared tomorrow, the smart contracts would continue functioning and payouts would still resolve via UMA.

The oracle question

The critical single design decision Polymarket makes is how markets resolve. The resolution oracle answers the question: when the event happens, who is the authoritative source of truth?

Polymarket uses UMA's optimistic oracle. Here's how it works:

  1. When resolution is due, anyone can propose the answer (e.g., YES, Swift announced tour dates on June 17).
  2. There's a dispute window (2–24 hours depending on market).
  3. If nobody disputes, that answer stands and payouts execute.
  4. If someone disputes, the question escalates to UMA's Data Verification Mechanism — holders of the UMA token vote on the answer. Voters are staked and can be slashed if they vote dishonestly.

This is called "optimistic" because most markets resolve without dispute — UMA's vote only triggers if someone puts money on the line to contest the proposed answer. Game theory argues that bad-faith proposers would lose to honest disputers over time.

The optimistic oracle has been criticized for handling edge cases poorly. In 2024, a handful of political markets had contested resolutions with visible community debate. Polymarket has responded by adding more explicit resolution criteria to markets — you'll see fine print like "Resolves YES if and only if AP declares the election on or before date X, otherwise NO" — which reduces ambiguity.

It's imperfect but it's the best system in production for decentralized prediction markets. Every other model (centralized operator, multi-sig, time-locked) has worse trade-offs.

Why Polymarket uses cryptocurrency

This is the question new users ask most often. If Polymarket is "just a prediction market", why does it need USDC, Polygon, wallets, and gas fees?

The answer has two parts.

Regulatory. Decentralized prediction markets are hard for any one jurisdiction to shut down. Polymarket is incorporated in the Cayman Islands and settles on Polygon; the exchange itself is not a US entity. When the CFTC sued Polymarket in 2022 it could only enforce against the US-facing website and the US-based company behind it, not the underlying contracts. Without crypto as the settlement layer, Polymarket would need bank partnerships in every jurisdiction it wanted to operate in, and most banks will not take the compliance risk of gambling-adjacent businesses.

Technical. The CLOB (central limit order book) that Polymarket operates needs to settle trades near-instantly at very low cost. Ethereum mainnet costs $5–$50 per trade; Polygon costs fractions of a cent. USDC is the dollar-pegged stablecoin that makes the prices human-interpretable (a 50¢ share is literally 0.5 USDC, not some volatile token denomination).

The downside is onramp friction. A new user has to figure out how to get USDC on Polygon — either via a centralized exchange like Coinbase that supports direct Polygon withdrawal, via MoonPay's fiat-to-crypto integration on Polymarket, or via a cross-chain bridge from Ethereum. Polymarket has invested heavily in fiat onramps to reduce this friction, but it's still a step that scares off casual users.

Who actually uses Polymarket

The user base is roughly three groups:

Crypto-native traders. These are the core users — people with USDC balances already, comfortable with wallets and gas, looking for alpha in event markets. They were on Augur before it died, on PredictIt before the CFTC squeezed it, and moved to Polymarket as it became the deepest book.

Political junkies and journalists. Drawn by the 2024 US election. Polymarket became the default cited source in major media (FT, NYT, WSJ) for real-time probability of outcomes. Most of these users are smaller traders who sized in for a few hundred dollars and sized out when the election resolved.

Sophisticated quantitative traders. The largest accounts on Polymarket run automated strategies — market-making, cross-exchange arbitrage against Kalshi and traditional sportsbooks, stat-arb against polling data. A handful of these accounts have moved nine-figure volumes.

Polymarket's total addressable market keeps growing because each of these groups expands as prediction markets become more mainstream.

What Polymarket is not

Several misconceptions worth correcting:

  • Polymarket is not a DeFi project in the yield-farming sense. You don't earn interest for holding positions. You make money only if you predict outcomes correctly.
  • Polymarket is not a casino. A casino has house edge. Polymarket is a peer-to-peer exchange — the house has no edge because there is no house.
  • Polymarket is not anonymous in the privacy-tech sense. Your wallet address is visible on-chain. Large positions are public. KYC is required for fiat withdrawal above certain thresholds.
  • Polymarket is not available in the US via the main app. After the January 2022 CFTC settlement, US IP addresses are blocked. See our country-by-country legality page for the current status.
  • Polymarket is not the same as Kalshi. Kalshi is a CFTC-regulated DCM available to US residents. Polymarket is decentralized and blocks US IPs. Here's the full comparison.

Fees, limits, and what things actually cost

Polymarket's fee structure:

  • Trading: 0%. You pay the difference between the bid and the ask (the spread), which is typically 1–3 cents on liquid markets and 5–10 cents on thin markets.
  • Polygon gas: ~$0.01 per trade. Imperceptible at normal trade sizes.
  • Deposit onramp: If you fund USDC via MoonPay or Onramper, expect 3–5% on the fiat-to-crypto conversion.
  • Withdrawal: Free to a Polygon wallet. For fiat withdrawal via Onramper, 1–3% + network fees.

Minimums: no minimum deposit. You can fund $5 and trade. Minimum trade size is typically a couple of USDC depending on the market.

Maximums: determined by market liquidity. On a deep market you can place five or six figures of orders without materially moving the price. On a thin market you'll eat through the book with a few hundred dollars.

Is Polymarket safe?

Three different "safe" questions people ask:

Custodial safety. Very good. Polymarket uses audited smart contracts on Polygon. Your USDC sits in a contract you control via your wallet; Polymarket Inc. cannot withdraw it. In the nuclear scenario where Polymarket Inc. shuts down, the smart contracts still function and markets still resolve via UMA.

Resolution safety. Good in normal cases, imperfect on edge cases. The optimistic oracle has resolved tens of thousands of markets without incident, but a handful of disputed political resolutions in 2024 showed that markets with ambiguous criteria can become contentious. Read resolution criteria before trading.

Legal safety. Varies by country. In the US, Polymarket access is blocked and using VPNs violates terms. In most of Europe, access is in a grey zone. In much of the developing world, access is legal by default because no local framework specifically covers crypto prediction markets.

For the full safety analysis see Is Polymarket safe? and Is Polymarket a scam?.

Comparison to major alternatives

  • Kalshi — US-regulated, CFTC-supervised, USD-native, no crypto. Smaller market selection but legal for US residents. Full Kalshi vs Polymarket.
  • PredictIt — academic-exempt US platform, $850 per-market cap, limited market set. Legacy player, declining relevance.
  • Manifold Markets — play-money prediction markets. Great for learning, no real stakes.
  • Augur — decentralized but effectively abandoned.
  • Betfair — UK-licensed betting exchange. Similar mechanics for sports, no political markets.

FAQ

Frequently asked questions

Can US residents legally use Polymarket?+

Not via the main app — Polymarket blocks US IPs following the 2022 CFTC settlement. US residents who want CFTC-regulated event contracts can use Kalshi instead, which is legal in all 50 states.

Is Polymarket a scam?+

No. Polymarket uses audited open-source smart contracts on Polygon, settles in a verifiable stablecoin (USDC), and has processed billions in volume without a hack. Read our full safety review.

Does Polymarket report my trades to the IRS?+

Polymarket itself does not issue 1099s. Any US user using Polymarket via VPN is responsible for self-reporting gains. For detailed tax guidance, see polytaxes.com.

How much does Polymarket charge in fees?+

A per-trade fee schedule applies (introduced in late 2025; historically 0%). You also pay the bid/ask spread (1–3 cents on liquid markets) and ~$0.01 in Polygon gas per trade. Fiat onramp via MoonPay costs 3–5%.

Can I use Polymarket on my phone?+

Yes, the Polymarket mobile app is available on iOS and Android. It supports all core trading features and links to external wallets.

What happens if the event is ambiguous at resolution?+

The optimistic oracle (UMA) handles disputes. If someone contests the proposed answer, UMA token holders vote. Most markets resolve without issue; ambiguous markets have resolution criteria spelled out in advance.

How do I get USDC on Polygon to trade?+

Three main paths: buy crypto on Coinbase and withdraw to Polygon, use the in-app MoonPay widget to buy USDC directly, or bridge from Ethereum via Polygon's native bridge.

Is there a minimum deposit?+

No. You can fund $5 and trade. Most liquid markets have minimum trade sizes of a few USDC.

Next steps

If you're new, the natural reading order is:

  1. What is a prediction market? — the academic and economic foundation.
  2. How does Polymarket work? — deeper technical walkthrough.
  3. Is Polymarket legal in my country? — regulatory status.
  4. How to sign up for Polymarket — step-by-step onboarding.
  5. Polymarket vs Kalshi — decide which fits you.

For the US-resident path, jump directly to our Kalshi guide.

Related reading

How does Polymarket work? A technical walkthrough

The full stack behind Polymarket: the order book, the smart contracts, the oracle, USDC settlement, and what happens from your click to final payout.

Polymarket vs Kalshi: the definitive comparison

Polymarket vs Kalshi, side by side. Fees, markets, regulation, UX, custody, taxes. The short answer: Kalshi if you're in the US, Polymarket if you're not. Here's the full reasoning.

Is Polymarket legal? Global legality explained (2026 update)

Polymarket's legality varies widely by country. It's blocked in the US, grey-zone in much of the EU, broadly accessible across Latin America, Asia, and Africa. Here's the full landscape.

How to sign up for Polymarket: the complete step-by-step guide

Create a Polymarket account in under 10 minutes. Full walkthrough covering email signup, wallet setup, USDC funding, and your first trade.

What is a prediction market? The complete primer

Prediction markets let people trade contracts on the outcome of real-world events, turning collective opinion into probabilities. Here's how they work, why economists love them, and what Polymarket and Kalshi bring to the category.