Kalshi achieved a new milestone last week by surpassing $4 billion in weekly virtual volume. For perspective, last year this number reached $54.5 million. This represents a growth of approximately 7,424%. However, beyond Kalshi’s own growth story, what is more interesting is the speed with which the platform closed the gap with rival Polymarket. In fact, even as recently as March of this year, the two leading prediction market platforms were close to a 50-50 split in weekly volume. Today, Kalshi processes 2.05 times what Polymarket does.
source: Artemis
The face that has stopped calm
In the same week that Kalshi recorded $4.1 billion in volume, Polymarket saw $2 billion. This represents a slight increase from the previous week but is still below the volumes seen during March and April. This trend has seen a noticeable shift in Kalshi’s favor since the last week of April, and part of this move is due to the V2 Polymarket upgrade rolled out on April 28, which was poorly received by users. The downgrade temporarily halted trading for about an hour and every open limit order on the platform was cleared at the same time. Users had to resubmit orders once the new system went live.
Volumes and user activity on the platform declined sharply after that. Monthly trading volumes fell for the first time in April after seven straight months of highs, and the number of traders fell about 12% between March and April, from about 733,000 to 643,000, Bloomberg reported. Cluster.
A Polymarket spokesperson directly attributed April’s volume drop to the upgrade, along with Vice President of Engineering Josh Stevens Bloomberg says“We let people down, and I won’t wear that.” Founder Shane Coplan went on to admit at an event at Harvard University that “there have been many times over the course of the business where the way the company was run was suboptimal.”
Kalshi’s single order book feature
Kalshi launched as a CFTC-regulated US exchange from day one, with every contract traded on a single, unified order book. Liquidity remains concentrated in one pool, keeping spreads tight and prices clean across markets.
Polymarket operates two parallel products. The global wallet-based platform on Polygon still serves international users and retains most of the historical volume. The newest US-facing product is operated through QCEX, a CFTC-regulated Polymarket venue It was acquired in July 2025 for $112 million It was relaunched for US users in December after receiving approval from the Commodity Futures Trading Commission (CFTC) as a brokerage exchange. The two products do not share liquidity, meaning that one Polymarket is effectively split across two separate order books with two different settlement layers.
For anyone operating at the current scale, this fragmentation represents a real point of friction. Kalshi doesn’t have it.
Distribution in the US is the other lever
Beyond the organization, the distribution group did the rest of the work. Calci contracts reach retail traders through Pricepeaks across 38 states, through Coinbase’s prediction markets integration, and through brokerage flows from Robinhood and Webull. On the institutional side, Clear Street joined as the exchange’s first FCM in May, opening access to institutional trading desks and ETF issuers.
DC wallpaper suits the picture. Kalshi just closed a $1 billion Series F at a $22 billion valuation led by Coatue, with the offering leaning toward annual trading volume now at around $178 billion and institutional flow up 800% in six months.
Polymarket, for its part, is still rebuilding its American footprint after being blocked from entering the United States for years. Today’s competitive picture looks less like two equal platforms and more like a local US exchange running away from a global platform trying to catch up at home. Whether this gap is permanent or a function of one-quarter execution is a question worth pursuing from here.
