On July 29, 2026, VolRoc recorded 177,064 active prediction markets across Kalshi and Polymarket, holding $1.40B in combined open interest. Day over day, active markets rose 8.9% and open interest rose 4.4% (vs July 28, 2026). Sports was the largest domain by open interest (36%), ahead of Politics & Elections (34%); together they accounted for 71% of all open interest. Kalshi carried 81% of active markets and Polymarket 19%.
Deterministic · template v1 · 2026-07-29
As of 2026-07-29 · 00:00 UTC
Active Markets
177,064
00:00 UTC freeze
Open Interest
$1.40B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
18,641
with trading activity
Kalshi / Polymarket
81% / 19%
by active-market count
Domain Composition — 12 domains
Sports
116,860
Other
24,562
Mixed / Multi-category
20,051
Politics & Elections
6,594
Entertainment & Culture
2,621
Crypto & Digital Assets
1,613
Companies & Business
1,379
Technology & AI
1,192
Economics & Inflation
971
Monetary Policy
460
World & Geopolitics
455
Climate & Weather
216
Science & Health
90
Venue-agnostic subject taxonomy from Kalshi series prefixes and
Polymarket title keywords. A residual Other bucket is reported honestly.
Yes-price across both venues, 10 buckets from 0 to 100. n = 177,064.
Largest Kalshi Series
Sports — multi-game parlays
94,235
Cross-category multi-markets
20,051
Midterm control
926
Music — artist streams
764
U.S. House races
601
Nextteamnba
479
NFL — next team moves
256
Nflwins
253
Mlbhr
244
Nextteammlb
235
Mlbhrr
208
Flprimary
201
Kalshi market families (Polymarket is not series-structured).
About & Citation
This is the fixed-hour (00:00 UTC) state of every active market on
Kalshi and Polymarket for July 29, 2026. The live
Observatory
shows the current diurnal value; this record is immutable. Open interest combines Kalshi
open interest with Polymarket USD liquidity as comparable USD magnitudes. Sources: Kalshi, Polymarket.
How to cite
“VolRoc Prediction Market Archive — July 29, 2026.” https://volroc.ai/prediction-markets/2026-07-29/
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