Kalshi posts a record ~$19B trading week as Polymarket US roughly triples its fall volume

Kalshi recorded its largest trading week on record at approximately $19B, according to DeFi Rate’s Oct. 12 snapshot. The report also pointed to growth at Polymarket US, where volume roughly tripled relative to its fall level.

Combination contracts drive Kalshi’s record

DeFi Rate attributed Kalshi’s weekly high to parlay-style combination contracts. That makes the product category central to the reported surge, rather than simply a backdrop to the platform’s overall activity.

Polymarket US also sharply increased its share, according to DeFi Rate. The available summary does not specify that share or identify the precise fall period used for the volume comparison.

The report was published Oct 12, 2026, at 9:54 PM ET. Its full source text was unavailable, leaving the headline and summary as the basis for these figures and limiting any further comparison between the platforms.

What it means for prediction markets

• Product mix matters: Kalshi’s approximately $19B record was driven by combination contracts; the available material does not establish how activity changed in other contract categories.
• Polymarket US is expanding its footprint: Roughly tripling its fall volume accompanied a sharp share increase, but the summary provides no exact share figure.
• The comparison remains incomplete: Without the underlying breakdown, the snapshot does not establish whether either platform’s growth will persist.