Kalshi and Polymarket volume spikes on McGregor vs. Holloway UFC 329 fight
Trading volume surged on Kalshi and Polymarket ahead of UFC 329, headlined by Conor McGregor's return against Max Holloway. McGregor opened as a heavy underdog on prediction markets despite the high-profile comeback. Both platforms offer event contracts on the fight, with active trading expected through the main event. The bout marks McGregor's long-awaited return to the octagon against the favored Holloway. Traders on both venues can buy contracts and exit positions early.
The UFC 329 volume test arrives right after DRW, Wintermute, and IMC build prediction market desks for Kalshi and Polymarket. Those desks promised to tighten spreads and absorb block-size flow. Now they must prove it under live sports load. For Kalshi, the timing is especially binding: its combo props and whale-marketing playbook need genuine book depth to back the large-wager visibility it promotes.
For Polymarket, billion-dollar revenue benchmarks set the liquidity standard that institutional allocators watch. If spreads widen or slippage surfaces on fight-night flow, both platforms lose credibility ahead of NFL and Olympics expansion. The first venue to publish per-market spread and depth data gains a competitive wedge. Until then, traders size in the dark, and institutional capital stays cautious.