The short answer: if you're a US resident who wants regulated, dollar-denominated event trading with normal tax paperwork, trade Kalshi. If you want the deepest global liquidity on crypto and international politics — and you're comfortable with a crypto-native stack — Polymarket is the bigger pond. Many serious traders use both and arbitrage the price differences between them.
The two platforms in one table
| Kalshi | Polymarket | |
|---|---|---|
| Regulation | CFTC-regulated US exchange (Designated Contract Market) | Crypto-native; re-entering the regulated US market via its acquisition of a CFTC-licensed exchange |
| Currency | US dollars | USDC (stablecoin) on Polygon |
| Custody | Brokerage-style account, USD in/out via bank transfer | Self-custody crypto wallet |
| US legal status | Fully legal for US residents | Historically blocked US users; US access returning through the regulated entity |
| Fees | Per-contract trading fee (scales with price; highest near 50¢), no gas | Typically no per-trade exchange fee; you pay spread and network costs |
| Taxes | US tax forms issued like other regulated trading venues | Your problem — crypto cost-basis accounting |
| Market coverage | US-centric: sports (the volume leader), politics, economics (CPI, Fed), weather, culture | Global politics, crypto, sports, world events |
| API | Free public REST + WebSocket API, official API keys | Public API + on-chain order book (CLOB) |
Regulation is the real fork in the road
Everything else follows from one difference. Kalshi is a Designated Contract Market overseen by the CFTC — the same regulator that oversees futures exchanges. Your balance is dollars, deposits come from your bank, and disputes have a regulator behind them. That's also why Kalshi could survive legal challenges and expand aggressively into sports event contracts, which now drive most of its volume.
Polymarket grew up offshore and crypto-native. It settled with the CFTC in 2022 and formally blocked US users for years — while remaining the world's largest prediction market by volume, especially during the 2024 election cycle. In 2025 it acquired QCEX, a CFTC-licensed exchange, as its path to serving US customers legally. The direction of travel is convergence: Polymarket is becoming more regulated, and Kalshi more expansive.
Practical consequence: for a US resident the compliant default is Kalshi today, with Polymarket's US offering worth watching as it matures.
Fees: the coin-flip tax vs the spread
Kalshi charges a trading fee per contract that scales with how uncertain the contract is — the fee is highest for contracts near 50¢ and shrinks toward the extremes. Frequent traders of coin-flip markets feel it; buy-and-hold traders of favorites barely notice it.
Polymarket generally charges no per-trade exchange fee. Your costs are the bid-ask spread, occasional network costs, and the on/off-ramp between dollars and USDC. For high-frequency strategies that difference matters; for occasional position-taking it mostly doesn't.
Liquidity and market selection
Polymarket's headline markets (major elections, geopolitics, crypto prices) are typically the deepest in the industry. Kalshi's edge is breadth in US-regulated niches nobody else can touch: CPI prints, Fed decisions, weather at specific airports, plus a sports book that has become its core business. Same-event prices on the two venues frequently diverge by a few cents — which is why cross-platform arbitrage tools exist.
The tooling ecosystem
Both platforms have grown real third-party ecosystems:
- Kalshi: a free public API with official keys makes bot-building straightforward — see our guide to the best Kalshi trading bots and tools. AI research services (including Kalmari, which publishes its full track record in public), no-code automation, screeners, and a healthy open-source scene.
- Polymarket: because every trade is on-chain, wallet-tracking and true copy-trading tools flourish — you can literally follow a specific profitable wallet. Alert bots, whale trackers, and Telegram terminals are abundant.
One structural difference worth understanding: Polymarket's transparency is per-trader (public wallets), Kalshi's is per-market (an anonymous order book). Copy-trading a real person is only possible on Polymarket; on Kalshi, "copy trading" means following a research service's published picks.
Taxes, briefly
Kalshi reports like a regulated US trading venue and issues tax documents. Polymarket positions are crypto transactions — every USDC round-trip is a taxable event you track yourself. If bookkeeping pain matters to you, this alone can decide the question. (Not tax advice; talk to a professional.)
So which should you trade?
- US resident, wants simplicity and legality: Kalshi.
- Global macro/crypto markets, deepest books, comfortable with wallets: Polymarket.
- Systematic trader: both — the cross-venue price gaps are themselves a strategy, and each platform's API supports automation.
- Just want researched picks in Telegram: that's what we build — Kalmari publishes AI research signals on Kalshi with a public, auditable record.
FAQ
Is Kalshi or Polymarket bigger? By global volume, Polymarket has generally led, driven by international users and marquee political markets. Kalshi is the larger regulated US venue and has grown explosively since expanding into sports.
Can I use both? Yes — nothing prevents holding accounts on both, and price divergence between them is a known trading strategy.
Which is safer? "Safer" means different things: Kalshi offers regulatory oversight and dollar custody; Polymarket's risks are crypto-stack risks (wallet security, stablecoin exposure). Counterparty risk on settled outcomes is low on both — resolution disputes are the thing to read up on for each platform.
Do both have trading bots? Yes. Kalshi's official API supports personal automation, and Polymarket's on-chain order book enables wallet-copying tools. Our bot roundup covers the Kalshi side in depth.