There are more prediction market platforms in 2026 than at any time in the industry's history — and they're not interchangeable. Kalshi and Polymarket each have billions in monthly volume but serve different user bases. PredictIt survived its 2022 near-death and runs a regulated niche. Manifold is a play-money market with real data. ForecastEx targets institutional use.
If you're picking a platform to trade, integrate with via API, or just understand the space, this guide compares them all on the dimensions that actually matter: liquidity, fees, geography, market depth, API access, and KYC.
We built ZenHodl to provide calibrated win probabilities for sports markets on Polymarket and Kalshi specifically, so we've integrated against most of these platforms. This is our working evaluation.
The Short Answer
| Platform | Best for | Monthly volume (est.) | Geography |
|---|---|---|---|
| Polymarket | US & international sharp traders, sports, politics | $500M-1B | Global ex-US (KYC) |
| Kalshi | US retail and regulated traders, sports events | $200-400M | US regulated |
| PredictIt | US politics enthusiasts, academic research | $5-10M | US regulated (CFTC) |
| Manifold | Forecasters who want a leaderboard, play-money only | N/A (play money) | Global |
| ForecastEx | Institutional event contracts | $20-50M | US institutional |
If you're in the US and want regulated access: Kalshi. If you're international or want deeper liquidity: Polymarket. If you want to practice without money: Manifold.
1. Polymarket (polymarket.com)
The largest prediction market by volume in 2026. Runs on Polygon blockchain. Markets are USDC-denominated binary contracts that settle based on real-world event outcomes (election results, sports outcomes, crypto prices, etc.).
| Dimension | Detail |
|---|---|
| Fees | 0% trading fee. ~0.5c spread + Polygon gas (~$0.01) |
| Liquidity | Highest in the industry. Large sports and political markets have $100k-1M+ depth |
| Market types | Binary (YES/NO). Event-driven. Expires at resolution |
| Resolution | Oracle-based (UMA) for subjective markets |
| Geography | Global, except US (enforced via geoblock; US users VPN regularly but violate ToS) |
| KYC | Required above $10k withdrawal, not required for normal trading |
| API | REST API with full order book depth. Reasonable rate limits. Documented |
| Best for | Sharp traders who need depth; bot developers; international users |
Strengths: Depth, speed (Polygon), no fees, programmatic access. The biggest liquid prediction market in the world.
Weaknesses: Not legal for US users (though widely accessed anyway). Oracle resolution can be contentious — some disputed markets in 2024-2025 became public disputes. Gas costs small but nonzero.
2. Kalshi (kalshi.com)
The CFTC-regulated US prediction market that won a landmark 2024 court case granting it the right to offer election event contracts. Now operates the largest US regulated prediction market.
| Dimension | Detail |
|---|---|
| Fees | Variable: 0-2c per contract depending on market. Higher than Polymarket for similar events |
| Liquidity | Deep on top-tier markets (elections, sports, Fed rates). Thin on long-tail |
| Market types | Binary YES/NO plus multi-outcome event contracts |
| Resolution | Kalshi's internal resolution team, regulated by CFTC |
| Geography | US only (domestic, regulated) |
| KYC | Full KYC required (SSN, bank linkage) |
| API | Full REST + WebSocket API with L2 order book. Well-documented |
| Best for | US retail; anyone needing CFTC-compliant event contracts; bot developers |
Strengths: Fully legal in US. Real money. CFTC regulation = consumer protections. Modern API. Growing fast (400%+ YoY volume through 2024-2026).
Weaknesses: Fees bite. KYC friction for new users. Less long-tail market coverage than Polymarket.
3. PredictIt (predictit.org)
The academic-pedigreed, long-running US political prediction market. Operated by Victoria University of Wellington's research program. Has been the most-cited academic prediction market since 2014.
| Dimension | Detail |
|---|---|
| Fees | 5% on profits, 10% withdrawal fee. Highest of any major platform |
| Liquidity | Thin. Many markets trade in $100-$1000 depth |
| Market types | Political events, some macro |
| Resolution | Manual by PredictIt team |
| Geography | US (and some international through compliance) |
| KYC | Medium — SSN required for US accounts |
| API | Simple API, limited documentation |
| Best for | Academic research; US political trading at modest scale |
Strengths: Longest continuous track record in the space (since 2014). Most-cited academic market. Safe haven for US political event contracts.
Weaknesses: Fees are aggressive. Liquidity caps at $850 per contract per user. Limited sports coverage. No real scale for algorithmic trading.
4. Manifold Markets (manifold.markets)
A play-money prediction market with a clever twist: real forecasters, real leaderboards, real skill-based currency (M$) that earns reputation and occasionally real prizes. No US geography issues because it's not real-money.
| Dimension | Detail |
|---|---|
| Fees | None (play money) |
| Liquidity | Good on popular markets. Thin on obscure ones |
| Market types | Binary, multi-outcome, numeric ranges, dependent markets |
| Resolution | User-created, typically self-resolved by creator |
| Geography | Global |
| KYC | None (play money) |
| API | Full REST API, free |
| Best for | Testing a strategy before committing real money; research; academic use |
Strengths: No geographic or KYC restrictions. Real signal quality on popular markets. Excellent for backtesting a forecasting strategy risk-free.
Weaknesses: Not a real-money market. No cash out. Forecasters are smart but incentives aren't money-aligned.
5. ForecastEx (forecastex.com)
A newer CFTC-regulated US institutional event-contract platform. Backed by Interactive Brokers. Launched 2024.
| Dimension | Detail |
|---|---|
| Fees | Institutional pricing. Not posted publicly |
| Liquidity | Building. Strong on macroeconomic events, thin elsewhere |
| Market types | Event contracts (binary and multi-outcome) |
| Resolution | Regulated |
| Geography | US institutional |
| KYC | Full — requires IB-style account with institutional verification |
| API | Via IB TWS API |
| Best for | Institutional and high-net-worth traders |
Strengths: Institutional-grade, CFTC regulated, IB backing. Most legitimate infrastructure of any platform.
Weaknesses: Not for retail. Not yet competitive on sports. Limited market coverage.
Side-by-Side: The Decision Matrix
If you're in the US and new to prediction markets
Kalshi. It's regulated, legal, and has the best UX of any US platform. Accept the fees as the cost of sleeping at night.
If you're experienced and want depth
Polymarket (if you're outside the US or willing to accept the gray zone). The fee advantage alone justifies it for active traders.
If you're building an algo trading bot
Kalshi or Polymarket — both have real APIs with real liquidity. We'd lean Kalshi if you're US-based and Polymarket if you're international. Avoid PredictIt for bots — the $850 contract cap makes scaling impossible.
If you want to practice without risking money
Manifold. Free, no KYC, real incentives (M$ reputation). The ideal backtesting sandbox.
If you're running an institutional strategy
ForecastEx. Regulated, connected to IB, institutional-grade.
The Sports Coverage Angle
Sports is where prediction markets are growing fastest in 2026. Current coverage by platform:
| Platform | NFL | NBA | MLB | NHL | CFB | Soccer | Tennis | eSports |
|---|---|---|---|---|---|---|---|---|
| Polymarket | ✓✓✓ | ✓✓✓ | ✓✓✓ | ✓✓ | ✓✓ | ✓✓ | ✓ | ✓ |
| Kalshi | ✓✓✓ | ✓✓✓ | ✓✓ | ✓✓ | ✓ | ✓ | — | — |
| PredictIt | — | — | — | — | — | — | — | — |
| Manifold | ✓ | ✓ | — | — | — | — | — | — |
| ForecastEx | ✓ | ✓ | — | — | — | — | — | — |
(Scale: ✓ = basic, ✓✓ = solid, ✓✓✓ = deep.)
Polymarket has the broadest sports coverage. Kalshi is catching up fast on NFL and NBA. For esports (CS2, LoL, Valorant), Polymarket is the only meaningful option.
Are Prediction Markets Actually Accurate?
The recurring question. The short answer is yes, but with caveats.
When they work well: Large, liquid markets with clear resolution criteria. Elections, major sports games, Fed rate decisions. Calibration on these is typically within 3-5% of the true outcome probability.
When they don't: Thin markets (under $10k depth), markets with ambiguous resolution, and markets where insider information could sway outcomes. On these, calibration can be 10-15% off.
From our own measurements using ZenHodl's calibrated model as the benchmark, Polymarket sports markets calibrate to within ~2-4% of our model's probabilities on high-volume NFL/NBA/MLB games. On low-volume college football games, calibration widens to 6-10%.
The Insider Question
You asked: are insiders exploiting prediction markets?
Honest answer: yes, occasionally. Every prediction market in history has had at least one market where someone with inside information moved the line. The 2024 PredictIt prediction of the Republican primary showed signs of inside-trader activity according to academic studies. Polymarket had public disputes over the 2024 US election resolution that implicated sophisticated actors.
The platforms' defenses are: - Kalshi: Manual surveillance + CFTC oversight - Polymarket: UMA oracle + community governance - PredictIt: Small trade limits
None of these are perfect. If you're trading prediction markets seriously, assume the line already reflects any public information (including "inside" info that's leaked publicly). Your edge has to come from quantitative modeling, not from being faster than the informed public.
Methodology and Bias Disclosure
This post is informed by our work building ZenHodl's sports prediction API. We have active integrations with Polymarket and Kalshi, and we've tested against Manifold. We're biased toward platforms with open APIs and CFTC regulation — the two dimensions most relevant to running a programmatic trading operation.
The "best" platform depends on what you're doing. If you just want to dabble in predicting elections from your couch, pick the one your neighbors use. If you're building a business, use this matrix.
Related Reading
If you're going deeper on prediction markets:
- How Prediction Markets Work for Sports — The 2026 beginner's guide explaining why prices are probabilities and why markets beat sportsbooks structurally.
- Can You Actually Win at Sports Betting Long Term? — The math of edge, vig, and the 52.4% threshold.
- The Complete Guide to Prediction Market APIs — Polymarket CLOB, Kalshi REST, The Odds API — with Python code for each.
- Calibrated Probabilities in Prediction Markets — Why calibration matters more than accuracy for trading.
- Kelly Criterion for Prediction Market Sizing — How to size positions given your edge.
- Polymarket Order Book Analysis — Spotting sharp traders in the book.
This guide is updated quarterly. Last verified: April 22, 2026. Volume estimates from public industry sources.