TLDR
- Kalshi and Polymarket recorded $1.44 billion in combined trading volume for September 2025, marking the highest monthly total for prediction market platforms
- Kalshi claimed 60% market share in September, reversing Polymarket’s earlier dominance through its Robinhood integration for sports betting
- Polymarket secured $2 billion from Intercontinental Exchange at $9 billion valuation, while Kalshi raised $300 million at $5 billion valuation
- Polymarket founder Shayne Coplan became the youngest self-made billionaire after the funding round
- Kalshi operates off-chain with API-only access, while Polymarket runs on-chain with transparent blockchain verification
Two leading prediction market platforms have shattered previous trading records. Kalshi and Polymarket generated $1.44 billion in combined trading volume during September 2025. The figure represents unprecedented growth for the prediction market sector.
The monthly volume demonstrates increasing mainstream adoption of prediction markets. Both platforms have attracted institutional backing in recent weeks. The funding rounds signal growing confidence in prediction market infrastructure.
Kalshi Overtakes Polymarket in Market Share
Kalshi captured 60% of the prediction market share in September. This marks a reversal from earlier in 2025 when Polymarket dominated. The shift occurred over several months.
The change stems from Kalshi’s partnership with Robinhood. Users can now place sports bets through Kalshi within the Robinhood app. This integration provides access to millions of retail investors.
Robinhood’s user base has helped Kalshi expand beyond crypto-native audiences. The platform now serves traditional retail traders. Sports betting functionality has driven user engagement.
Polymarket previously held the leading position in prediction market trading. The platform’s September performance still contributed substantial volume. Both platforms are experiencing growth despite the market share shift.
Major Funding Rounds Value Platforms at Billions
Polymarket raised $2 billion from Intercontinental Exchange last week. ICE owns the New York Stock Exchange. The investment values Polymarket at $9 billion.
Kalshi secured $300 million in its recent funding round. The raise values the platform at $5 billion. Both valuations reflect institutional interest in prediction markets.
Bloomberg reported that Shayne Coplan became the youngest self-made billionaire. The Polymarket founder reached this status following the $2 billion raise. His stake in the company pushed his net worth past the billion-dollar mark.
The combined $2.3 billion in funding represents one of the largest capital influxes into prediction markets. ICE’s involvement brings traditional finance expertise to the sector. The exchange operator’s investment validates the prediction market model.
Platform Architecture Differs on Transparency
Kalshi and Polymarket use different technical infrastructures. Kalshi operates off-chain with traditional API access. Users and observers must rely on the platform’s reported data.
Some analysts have raised questions about independent verification of off-chain data. The API-only model limits outside confirmation of trading volumes. Kalshi’s figures cannot be verified through public blockchain explorers.
Polymarket runs entirely on-chain. All markets and trading positions are visible on the blockchain. Anyone can verify activity through blockchain explorers.
The on-chain architecture provides transparency advantages. Users can independently confirm trading volumes and market data. This approach aligns with crypto-native principles of verifiable information.
Both platforms continue to grow despite architectural differences. Kalshi prioritizes accessibility through mainstream partnerships. Polymarket emphasizes transparency through blockchain technology.
The September trading volume reflects increased user participation across both platforms. Prediction markets are expanding beyond election forecasting into sports betting and other categories. The $1.44 billion monthly total exceeds all previous records for the sector.
