Polymarket vs Kalshi (2026): Fees, API, Latency & Automation

Most "Polymarket vs Kalshi" comparisons are written for someone deciding where to place a bet. This one isn't. If you're building an automated strategy — a market-making bot, a cross-platform arbitrage engine, or a latency-sensitive scalper — the questions that actually matter are different: Is there a real public API? How are makers treated on fees? Where do the servers live? What order types can you use?

Here's the short version. Polymarket is a crypto-settled, order-book exchange with a mature developer API, maker-friendly economics, and infrastructure in the EU — it's the better home for automated, latency-sensitive, maker-side strategies. Kalshi is a CFTC-regulated US exchange with clean legal access in all 50 states and a solid API, but a flatter fee model and a US-centric footprint. The right choice depends on where you trade from, whether you need US regulatory cover, and which side of the book you live on.

Polymarket vs Kalshi at a glance

Everything below expands on the rows that matter most for automated trading. For current fee percentages and latency figures, always check the primary docs linked in each section — those numbers move.

Regulation, US access & KYC

This is the part every comparison covers, so we'll keep it tight — but it's a real constraint on where your bot can legally run.

Kalshi: regulated, US-wide, KYC required

Kalshi is a CFTC-regulated Designated Contract Market. It's available across all 50 US states, deposits are in USD, and every account goes through KYC/AML. For a US-based trader who wants regulatory certainty and a clean tax and banking trail, that's the whole pitch.

Polymarket: no-KYC outside the US, KYC on the US exchange

Polymarket's international exchange — the one with the deepest liquidity — requires no KYC: outside restricted regions you can sign up with an email, get a wallet generated for you, deposit USDC, and trade. That international exchange is geoblocked for US IP addresses, and routing around it with a VPN is a terms violation that can freeze funds, not a workaround. A separate CFTC-regulated Polymarket US exchange opened to US users in 2026 and does require KYC. Confirm the current US status on Polymarket before relying on it.

Bottom line for bots: if you need US regulatory cover, Kalshi is the simpler path. If you're outside the US and want frictionless, no-KYC programmatic access, Polymarket's international exchange is hard to beat.

Fees & maker economics

For automated strategies, fees aren't a footnote — they're the difference between a profitable market maker and a slow bleed. The two platforms think about makers very differently.

Kalshi: a flat taker formula

Kalshi charges takers on a formula that scales with price — fees are highest for contracts trading near 50¢ and fall toward the extremes. Maker treatment varies by market. The exact schedule is published in the Kalshi fee documentation; verify the current numbers there before modeling a strategy.

Polymarket: makers get paid

Polymarket uses a category-based taker fee (lower on categories like politics and finance, higher on crypto), and crucially makers pay $0. On top of that, resting limit orders are eligible for two separate incentive programs:

• Maker rebates — a share of the taker fees your filled orders generate, paid out in USDC.
• Liquidity rewards — a separate daily program that pays makers for keeping two-sided orders near the midpoint, scored quadratically so precision is rewarded.

See the maker rebates program and liquidity rewards docs for the current formulas.

What this means for market-making and HFT

If your strategy is maker-heavy — posting two-sided quotes and earning the spread — Polymarket's structure is materially better: you're paid to provide liquidity rather than charged for it. Kalshi's flat model is simpler to reason about but doesn't reward makers the same way. For a deeper treatment of quoting strategy, see our guide on market making on Polymarket (coming soon).

APIs & automation — the part nobody else compares

This is where a trader-focused comparison earns its keep. Both platforms are programmable, but the developer experience differs.

Polymarket: a full CLOB API + official SDKs

Polymarket exposes a CLOB API with both REST (order placement, order book snapshots) and WebSocket (real-time order book and user channels). Alongside it sit the Gamma API for market metadata and discovery and a Data API for positions and history. Official clients cover Python (py-clob-client), TypeScript, and Rust, so you can sign EIP-712 orders and stream the book without writing the plumbing yourself. Our CLOB API guide (coming soon) walks through auth and your first order.

Kalshi: a WebSocket-first REST API

Kalshi offers a public REST and WebSocket API with authenticated order placement. Its real-time design is WebSocket-forward — order-book deltas, fills, and positions arrive over dedicated channels. Official first-party SDK coverage is thinner than Polymarket's, so many builders wrap the REST/WS endpoints themselves.

Order types compared

Your execution logic is only as good as the order types available:

• Polymarket: GTC (good-till-cancelled), GTD (good-till-date), FOK (fill-or-kill), FAK (fill-and-kill).
• Kalshi: IOC (immediate-or-cancel), end-of-day, and custom expirations.

The GTC/GTD split on Polymarket suits resting maker strategies; Kalshi's IOC-style controls suit opportunistic takers. Match the platform to how your bot actually places orders.

Can you run bots on both?

Yes — both platforms are built to be traded programmatically. For a step-by-step walkthrough on Polymarket, see our guide on how to build and deploy a Polymarket trading bot. The practical question is where the bot runs, which brings us to infrastructure.

Latency & infrastructure

For anything time-sensitive — arbitrage, news-driven repricing, short-duration crypto markets — the physical distance between your bot and the matching engine is a real edge.

Where each platform runs

Polymarket's core trading infrastructure is hosted in AWS eu-west-2 (London). That means a bot running in or near the EU reaches the order book far faster than one calling in from a US home connection. Kalshi's footprint is US-centric, so the geography flips: US-hosted infrastructure has the advantage there.

Why server location matters

When news breaks, prediction-market odds move within seconds, and the orders closest to the matching engine fill first at the best prices. A market maker without low latency gets adversely selected; an arbitrageur a few hundred milliseconds too slow watches the gap close before the fill lands. Polymarket even introduced dynamic taker fees on its 15-minute crypto markets specifically because latency arbitrage was so dominant.

The takeaway: co-locate your bot with the exchange you're trading. For Polymarket that means EU-hosted infrastructure close to London — not a laptop on a home connection. This is exactly the gap PolyCLOB closes: a low-latency, no-KYC runtime that sits next to Polymarket's CLOB, so you skip the VPS setup and deploy close to the order book. See the features for specifics, or our server-location and latency guide (coming soon) for measured benchmarks.

Liquidity & execution quality

Fees and latency don't matter if you can't get filled. Liquidity determines your real, all-in cost through spreads and slippage.

Polymarket generally offers deeper books and tighter spreads across its strongest categories — politics, crypto, and global events — which means less slippage on size and less price impact when you move. Kalshi's liquidity is strongest on US sports and regulated US event markets, where it can be the more active venue; on thinner secondary markets, spreads widen and fills get harder on either platform.

For execution-sensitive strategies, benchmark the specific markets you trade rather than trusting a platform-wide average — depth varies enormously between a flagship election market and a long-tail contract.

Which should you use?

There's no single winner — it depends on your strategy and where you sit:

• US trader who needs regulatory cover: Kalshi. Legal in all 50 states, USD banking, clean compliance.
• Non-US, automation-first trader: Polymarket. No-KYC access, mature API, deeper liquidity.
• Market maker / liquidity provider: Polymarket. You're paid via rebates and liquidity rewards instead of charged.
• Cross-platform arbitrageur: Both — the whole point is pricing the same event on each venue. See Polymarket arbitrage bots (coming soon).
• Latency-sensitive / short-duration crypto trader: Polymarket, with EU-hosted infrastructure near London.
• US sports bettor: Kalshi, for its sports depth and legal access.

Many serious operators run on both, sizing capital to where each platform's fees, liquidity, and latency favor their strategy.

FAQ

Is Polymarket legal in the US?

Polymarket's no-KYC international exchange is geoblocked for US IP addresses. A CFTC-regulated Polymarket US exchange opened to US users in 2026 and requires full KYC. Using a VPN to reach the international exchange violates the terms and risks frozen funds.

Does Kalshi have an API?

Yes — Kalshi offers a public REST and WebSocket API with authenticated order placement, suitable for automated trading. Its real-time design is WebSocket-first.

What are Polymarket maker rebates?

Makers pay no fee and can earn a rebate — a share of the taker fees generated by their filled resting orders — plus separate daily liquidity rewards for quoting near the midpoint.

Which has lower latency for bots?

It depends on where your bot runs. Polymarket's matching infrastructure is in AWS eu-west-2 (London), so EU-hosted bots reach it fastest. Kalshi is US-centric, so US-hosted bots have the edge there.

Can you build trading bots on Polymarket and Kalshi?

Yes on both. Polymarket exposes a CLOB API with official Python, TypeScript, and Rust clients; Kalshi exposes a REST and WebSocket API. Both support programmatic order placement.

Which platform has better liquidity?

Polymarket generally has deeper liquidity and tighter spreads across politics, crypto, and global events, while Kalshi is strongest on US sports and regulated US markets.