The guide
Kalshi and Polymarket are the two biggest prediction markets, and they look alike from the outside: yes/no shares between 0¢ and 100¢, where the price is the implied probability and a winning share pays $1.00. Under the hood they are built very differently — and that changes what you can trade, what you pay, how a market is settled, and above all how much you can see about who is trading. Here is the comparison.
Kalshi vs Polymarket at a glance
| Polymarket | Kalshi | |
|---|---|---|
| Structure | On-chain market — positions are tokens on Polygon | CFTC-regulated exchange (a designated contract market) |
| Money | A dollar stablecoin, held in your own wallet | US dollars, held by the exchange |
| How prices form | Central limit order book | Central limit order book |
| Resolution | UMA optimistic oracle, with an on-chain dispute window | The exchange, under each contract's rules |
| Fees | None on most markets; a taker fee on some | On most trades, largest near 50¢ |
| Who is trading | Public — every fill is on-chain | Private accounts |
| Smart-money tracking | Yes — wallet P&L, ranks, holders | Not possible from public data |
How they're built
- Kalshi is a US-regulated exchange (a CFTC-regulated DCM). Trades settle on its own books in dollars, with the structure and oversight of a traditional exchange.
- Polymarket's main platform is an on-chain market: trades settle on Polygon, positions are tokens in your own wallet, and every fill is a public blockchain event. That's the defining difference. (Polymarket also runs a separate US-regulated venue for US users; this comparison is about the on-chain platform.)
The odds work the same on both — if that part is new, start with how Polymarket odds work.
Fees and resolution
Most Polymarket markets charge no trading fee (some market types carry a taker fee); Kalshi charges a fee on most trades, scaled so it is largest for contracts priced near 50¢. Both change their schedules, so check the current ones before trading size. Resolution differs too: a Kalshi contract is settled by the exchange under its written rules, while a Polymarket market resolves through the UMA oracle — anyone can propose the outcome, and a wrong proposal can be disputed on-chain before it settles.
Why on-chain settlement is the big one
Because every Polymarket trade is on-chain, the entire market is analyzable. You can rebuild any wallet's real profit from its fills, rank 200k+ traders, detect bots, and watch smart money move in real time — none of which is possible on a venue that settles privately. This is exactly what Polynyx does: the leaderboard, the smart-money tracker and the model all exist becausethe data is public. On a closed exchange, there's no equivalent view of who's winning.
What you can trade
Both cover politics, economics, sports and world events; availability and the exact market menu differ by platform and by your jurisdiction. Polymarket's range spans sports, esports, crypto, politics and economics, which you can browse live on the markets page. For how either compares to a bookmaker, see Polymarket vs a sportsbook.
The bottom line
If you want the oversight of a US-regulated exchange, that's Kalshi's pitch. If you want depth, breadth and full transparency into who's trading and how they've done, Polymarket's on-chain data is unmatched — and Polynyx Premium (from $15.00/mo) turns that data into names, ranks and P&L of every smart wallet, model picks and unlimited portfolio tracking. Builders can access the same data via the Polynyx API and MCP server.
Polynyx is independent analytics for Polymarket data, not affiliated with Polymarket or Kalshi, not a betting operator, and nothing here is financial advice. Platform availability and eligibility depend on your jurisdiction.
Common questions
What is the difference between Kalshi and Polymarket?
Kalshi is a CFTC-regulated exchange: trades settle in US dollars on its own books and accounts are private. Polymarket's main platform is on-chain: positions are tokens on Polygon, markets resolve through the UMA oracle, and every trade is public — which is what makes wallet-level analytics like Polynyx possible.
Are Kalshi and Polymarket odds the same?
Usually close on the same event, because traders arbitrage large gaps away. They can still differ by a few points — fees, liquidity, how each contract is worded and resolved, and who trades on each venue all move the price.
Which has lower fees, Kalshi or Polymarket?
Most Polymarket markets charge no trading fee, though some market types carry a taker fee. Kalshi charges a fee on most trades that is largest for contracts priced near 50¢. Both publish their schedules and change them over time, so check the current ones before trading size.
Can you see who is trading on Kalshi?
No. Kalshi accounts are private, so there is no public record of who holds what. On Polymarket every fill is a public blockchain event, so you can rebuild any wallet's profit, rank traders and see which side the profitable wallets hold.