Washington, United States - August 28, 2026
As prediction-market activity reaches new highs and regulators intensify scrutiny, a fresh data service is making it easier to compare identical questions listed on different platforms. Predictions.io now aggregates more than 9,700 event pages from Kalshi, Polymarket and Manifold and has published free utilities that let users calculate venue fees and convert odds formats.
The timing comes as the three largest prediction venues recorded combined July volume of $50.59 billion, with Kalshi representing roughly 74.5% of that total. The sector has drawn a series of regulatory actions: New York City launched an inquiry into the leading venues; a Washington judge ordered Kalshi to stop most wagers within the state; and the Commodity Futures Trading Commission initiated an internal review of so-called "mention markets." These developments underscore why transparent cross-venue price data may be valuable to traders and journalists alike.
Price divergence on identical questions
Predictions.io highlights that when two platforms list the same, word-for-word question, their prices can differ materially. On directly comparable midterm markets tracked by the service, the question "Blue tsunami in 2026?" showed a 44.5% price on Polymarket and 36.0% on Kalshi. Another identically worded question, "Blue wave in 2026?", was quoted at 82.5% on one venue and 74.0% on the other. Both examples reflect an 8.5 percentage-point gap.
Across a sample of binary markets that appear on multiple venues, Predictions.io reports a median gap of more than four percentage points; nearly half of the paired markets had differences of five points or greater. The prices cited were current as of 05:08 UTC on 28 August 2026, and the site displays both venues' live prices side by side for direct comparison.
"A single venue's price is a data point. The spread between venues is the information. When the two biggest markets in the world disagree by seven points on the same sentence, that disagreement is the story - and nobody who runs one of those markets is in a position to report it." said a spokesperson for Predictions.io.
What Predictions.io provides
The platform matches equivalent questions across Kalshi, Polymarket and Manifold so users can view the same event across venues. It organizes more than 9,700 event pages into 23 categories that include US politics, economics, crypto, sport and geopolitics.
Predictions.io also published two free tools:
- Fee Calculator - Input a trade to see the fee, total outlay and effective all-in price on each venue, accounting for Kalshi's 0.07 × P × (1−P) taker formula and maker discount and contrasting that with Polymarket's zero-fee standard markets. The tool is available at https://predictions.io/tools/fee-calculator.
- Odds Converter - Convert between American, decimal and fractional odds, see implied probability and prediction-market prices, and view the vig-free line. The converter can be found at https://predictions.io/tools/odds-converter.
A live venue comparison page that juxtaposes Kalshi and Polymarket is online at https://predictions.io/compare/polymarket-vs-kalshi, and live midterms markets are surfaced at https://predictions.io/lobby/us-politics.
Business model and contact information
Predictions.io states that it does not operate any market and takes no position in any contract. The service is described as a data and comparison provider rather than an exchange, broker or investment adviser. Users seeking more information can contact the platform at [email protected], and social links are listed at https://bio.site/predictions.io.
This launch arrives at a moment when prediction markets are simultaneously expanding in volume and facing intensified regulatory attention. By collecting and aligning questions across venues, Predictions.io aims to make inter-venue spreads visible to traders, journalists and other market observers.