Polymarket vs Kalshi Features and Key Differences

same events, different prices. buy yes on one, no on the other, lock in the spread.

been doing this for 6 weeks now. was trying to do it manually at first but by the time you switch tabs the gap is gone.

started using arbpoly to automate it. executes on solana so its actually fast enough to catch them. running about 10k, pulling $300-400/week depending on how many spreads hit. last week was crazy with all the political markets.

anyone else here doing cross-platform arb or everyone just trading kalshi direct? curious what returns people are seeing.

I’ve been running a scanner on Polymarket vs. Kalshi for the last 48 hours, and the inefficiencies are actually insane.

I'm consistently finding 4-6 cent spreads on identical events (Fed rates, Nominations) expiring within 24-48 hours.

The markets are totally fragmented. I built a quick TypeScript engine (pmxt) to aggregate the order books in real-time so I can snipe them before the gap closes.

I just open-sourced the scanner if anyone wants to run it themselves:

For those of you already doing this, are you hitting liquidity ceilings on Kalshi? I'm trying to scale this up, but the fill rates on the US side are annoying.

• Sports: $2.28B (72.4% market share) vs $871M (27.6% market share)
• Politics: $72M (15.9% market share) vs $385M (84.1% market share)
• Crypto: $495M (61.3% market share) vs $312M (38.7% market share)
• Economy & Financials: Kalshi: $13.3M (34.8% market share) vs $24.9M (65.2% market share)

Kalshi is dominating

OC:

a World Cup hangover means a chance to assess prediction markets' biggest rivalry. Polymarket (US+intl) vols are down ~56% from a June record, while Kalshi is down ~25% since its own peak. that's not good news for the company that held 98% market share pre-2024 US election.

Polymarket's attempts to recover lost ground so far, millions in liquidity rewards, influencer schemes, limited parlays, haven't succeeded. Crypto price markets, still among the hottest bets on its site, now trail Kalshi's volumes after a flippening in April.

Source (Bloomberg)

Depends where you live and if you like crypto

I have been trading in prediction markets for two days and have created a Polymarket account. Does anyone have experience with Polymarket and Kalshi and can explain the difference of both platforms to me? At first glance, they look very similar.

Many of that would do it are not able to create account with Kalshi, there have been some really nice arbs on Kalshi tbf

Also when it comes to "market inefficiencies" liquidity and time decay are important factors

If you find arb that pays you 3-4% but you need to wait year for it to resolve it's effectivally worth 0% in reality because in year time inflation alone will likely be over 4% meaning even if you make that 3-4% you lose money on inflation/risk free rate

Seems like the arb ops lack the liquidity to be very profitable. Might indicate larger ones are being controlled by private arb bots already.

I'm curious how everyone here researches prediction markets.

Do you mostly stick with the native Polymarket/Kalshi interfaces, or do you use other tools as well?

For example:

• Tracking large traders or wallet activity
• Finding markets with unusual price movement
• Comparing the same market across platforms
• Keeping track of your own performance
• Testing strategies before risking real money

Is there a website, dashboard, spreadsheet, or workflow you couldn't trade without?

And if you could have one new feature or tool for prediction markets, what would it be?

The issue is Kalshi account can’t be created from lot of countries with proper ID. Polymarket is anonymous

I just signed up on Kalshi and am very happy I found it. I plan to use it mostly for actual investment hedging. I'll plan to keep using my bookie for sports betting for now. Dude has treated me well after all.

I don't care about how the make money behind the scenes. As long as I understand what I'm doing and they provide the service I'm looking for I am happy. They can front run, back run me or sell my order flow (or whatever) so that's all I care about.

So why chose Polymarket over Kalshi? I gave them 5 stars because I went from app download to my first prediction in less than 5 minutes! So, educate me! And any recommendations on subreddits

where should one base their AWS server for Polymarket arbitrage

Polymarket is better for political events / crypto token movements

Kalshi is better for sports imo

Similar structure but better liquidity in different areas

I’ve been using Robinhood prediction market but it’s limited to a few bets. Trying to switch either to Kalshi or Polymarket. Any feedback as to which is better?

Nobody really knows but Robinhood is slowly sneaking into the Duopoly as a contender. I prefer Polymarket at the moment but being in USA, only have Sports atm.

The experience you get from both platforms varies depending on your risk profile and how much you understand about what's actually happening behind the scenes.

Both Kalshi and Polymarket use P2P, so you are trading against other users, not the platform.

For example, sportsbooks limit and ban winning players. P2P prediction markets don't. So all the traders and professionals can stay on the platform indefinitely. Every time a casual user opens a position, there's a decent chance a full-time trader is on the other side.

P2B platforms work more like a traditional sportsbook, but the platform controls the margin, and you're playing against the house edge rather than against professionals.

Furthermore, Kalshi is centralised: traditional order book, fiat currencies, regulated company. You're trusting an institution.

On the other hand, Polymarket is decentralised: blockchain-based, crypto-native, automated market makers, no central authority. Nobody can manipulate the book.

If you came from sports betting, jumping straight into P2P order books without understanding the difference is genuinely one of the main reasons people underperform here.