- What: Polymarket is a peer-to-peer prediction exchange on Polygon where YES/NO shares trade between $0 and $1 — the price is the crowd's live probability estimate for any event.
- Why it matters: Unlike bookmakers, no house sets the odds — prices emerge from real traders risking real USDC, making them among the most accurate public forecasts available.
- Key number: Polymarket processed over $3 billion in trading volume in 2024–2025, with individual fees under 2% round-trip on liquid markets.
- Bottom line: Learn the CLOB order book, UMA oracle resolution, and bid-ask spread mechanics before trading — these three things determine every cent you make or lose.
What Is Polymarket?
Polymarket is the world's largest prediction market — a platform where people trade real money on real-world event outcomes. The prices those trades create become some of the most accurate probability forecasts available anywhere.
It runs on the Polygon blockchain (a fast, low-fee network built on top of Ethereum) and uses USDC (a digital dollar — 1 USDC always equals $1) as its currency. In 2024–2025 it processed over $3 billion in trading volume and became a go-to forecasting reference for the New York Times, the Economist, and major financial institutions.
Unlike a bookmaker who sets the odds and takes a house edge, Polymarket is peer-to-peer: every trade happens between two people with opposing views. When you buy YES at 65¢, you're buying from someone selling YES (taking the NO side) at 65¢. The market's price at any moment reflects the collective probability estimate of everyone trading it.
How Prices Are Set: The CLOB Order Book
Polymarket uses a Central Limit Order Book (CLOB) — the same matching system used by stock exchanges like NASDAQ. Buyers and sellers post their prices, and trades happen automatically when they match. The CLOB runs off-chain for speed but settles on-chain for full transparency.
Market orders vs. limit orders
You can place two types of orders:
- Market order: Buy or sell immediately at the best available price. Fast, but you may pay slightly more (or receive slightly less) than the current mid-price.
- Limit order: Set the exact price you're willing to pay. Your order sits in the queue until someone takes the other side. Better price control, but no guarantee of execution.
Reading the spread
The spread — the gap between the best bid (what buyers will pay) and best ask (what sellers want) — tells you exactly how liquid a market is and what your effective cost is to enter and exit.
| Spread | Market quality | Example |
|---|---|---|
| < 1¢ | Excellent — enter/exit easily | Major election markets |
| 1–3¢ | Good — normal for most active markets | BTC price milestones |
| 3–7¢ | Fair — factor into your EV calculation | Smaller policy markets |
| > 7¢ | Thin — high effective cost | Obscure niche markets |
Our Poly-Sim Score automatically factors spread into every market's rating — you can filter to only see markets where the spread doesn't kill your edge.
Your Money on Polymarket
All trades use USDC — a digital dollar issued by Circle, fully backed 1:1 by US dollars held in reserve. This means your P&L is always denominated in dollars, immune to crypto price swings affecting your account balance.
Polygon network fees are typically under $0.01 per transaction — effectively zero relative to any meaningful trade size. When you win, USDC is sent to your wallet automatically the moment the market resolves.
How to fund your Polymarket account
Polymarket doesn't accept credit cards or bank transfers directly. You need USDC on the Polygon network. The most common routes:
- Fastest: Buy USDC on Kraken via ACH (free in the US), withdraw directly to Polygon. Total cost: ~$0.90 flat withdrawal fee.
- If you have ETH/BTC: Use our instant exchange tool to swap to USDC, then bridge to Polygon via the official Polygon Bridge.
- Via Polymarket's onboarding: Polymarket has a built-in fiat onramp via MoonPay. Convenient but carries a 2–4% conversion fee.
How YES and NO Shares Work
Every Polymarket market has two complementary tokens: YES and NO. They are priced so that YES price + NO price ≈ $1.00 (slight deviations occur due to spreads).
If YES is priced at 65¢, the market is saying there's a 65% implied probability the event happens. If you believe the true probability is higher — say, 80% — you have a positive-expected-value opportunity to buy YES.
| Scenario | Your position | Event outcome | Result |
|---|---|---|---|
| Buy 100 YES @ 65¢ | $65 invested | Event happens | +$35 profit (35¢ × 100 shares) |
| Buy 100 YES @ 65¢ | $65 invested | Event doesn't happen | −$65 (total loss) |
| Buy 100 NO @ 35¢ | $35 invested | Event doesn't happen | +$65 profit |
| Buy 100 YES @ 65¢, sell @ 80¢ | $65 invested | Exit before resolution | +$15 profit (exit pre-resolution) |
How Markets Resolve: The UMA Oracle
Polymarket resolves markets using the UMA Protocol's Optimistic Oracle — a decentralised truth-verification system where no single person or company decides outcomes. The process is transparent and dispute-resistant:
Market expiry
The market's end date passes. Trading halts automatically.
Outcome submitted
Anyone (typically Polymarket or a designated resolver) submits the outcome, staking UMA tokens as a bond to vouch for accuracy.
Dispute window (2 hours)
Any UMA token holder can dispute the submitted outcome by staking a counter-bond. This triggers a community vote.
Resolution
If undisputed, the market resolves automatically. If disputed, UMA token holders vote on the correct outcome over 48–72 hours. The losing party forfeits their bond.
Payouts
Winning shares redeem for exactly $1.00 USDC each. Losing shares expire at $0. USDC is sent directly to your wallet.
Fees — What Polymarket Actually Costs
Polymarket's fee structure is simple and competitive: 2% of net winnings at resolution. Nothing else.
- No fee to place orders
- No fee to cancel or modify orders
- No deposit or withdrawal fees (just Polygon gas, typically <$0.01)
- No subscription or account fee
You buy 1,000 YES shares at 60¢ — investing $600. The event happens and you receive $1,000. Net profit = $400. Polymarket fee = $400 × 2% = $8. Net take-home = $392.
Compare this to traditional prediction markets and sports books, which embed a 5–10% overround (house edge) into every odds price. Polymarket's 2%-on-winnings structure is far more favourable for skilled traders.
Liquidity and Market Quality
Polymarket's liquidity varies enormously by market. Understanding this is critical for execution quality:
- Major political markets (US elections, EU policy) — $5M–$50M open interest, spreads under 0.5¢. Professional market makers provide tight quotes 24/7.
- Active crypto markets (BTC price, ETH price milestones) — $1M–$10M open interest, typical spreads 1–2¢.
- Niche or new markets — Often thin with $10k–$100k open interest and spreads of 5–15¢. High slippage risk on larger positions.
As a rule: never place a market order larger than ~2% of the visible order book depth without checking what price you'll actually receive. Use limit orders for any position over ~$500.
How poly-sim.com Enhances Your Polymarket Edge
poly-sim.com reads Polymarket's public data in real time and turns it into actionable intelligence — all free, no account required:
- Poly-Sim Score — every live market rated 0–100 for edge, value, and information quality. Filter to your highest-probability opportunities instantly.
- Hall of Whales — see every large trade ($5k+) the moment it hits the chain, and which wallets have positive long-term P&L.
- Ripple Effect — finds markets that are lagging behind news already priced elsewhere. Arbitrage signal, live.
- Whale Analytics — 11 charts tracking smart-money positioning, market concentration, and whale win rates.
- Wallet Tracker — paste any Polymarket wallet address to see their complete trade history, P&L, and strategy patterns.
- Global Pulse — world map of live geopolitical prediction market odds.
Frequently Asked Questions
Is Polymarket legal?
Polymarket is legal in most countries. It operates as a decentralised protocol on Polygon blockchain — no central authority controls it. US persons are currently geo-blocked at the interface level due to CFTC regulations (Polymarket paid a $1.4M CFTC fine in October 2022 and implemented US geo-blocking). Users in Europe, UK, Canada, Australia, and most of the world can access Polymarket freely.
Is Polymarket available in the US?
No. Polymarket is geo-blocked for US residents and prohibited by its Terms of Service from US participation. US residents should not use VPNs to circumvent this restriction, as it would violate the Terms of Service.
How liquid is Polymarket?
Liquidity varies significantly. Major political markets can have $10M–$50M in open interest with very tight spreads. Niche markets may have thin order books. Use our Poly-Sim Score to check volume, spread, and edge-adjusted ratings before entering any position.
Can I short a market on Polymarket?
Effectively yes — by buying NO shares. If YES is at 70¢, NO is at 30¢. Buying NO profits if the event doesn't happen. This is equivalent to shorting the event. You can also sell YES shares you already hold to exit or partially reduce a position.
What happens if a market resolves N/A (ambiguous)?
If the UMA oracle determines a market's resolution criteria were ambiguous or the event outcome cannot be clearly determined, the market may resolve N/A. In this case, all participants receive their invested USDC back minus a small administrative fee. This protects against poorly-worded market resolutions.