On June 28, 2026, VolRoc recorded 219,824 active prediction markets across Kalshi and Polymarket, holding $2.36B in combined open interest. Day over day, active markets rose 4.6% and open interest rose 1.9% (vs June 27, 2026). Sports was the largest domain by open interest (51%), ahead of Politics & Elections (16%); together they accounted for 67% of all open interest. Kalshi carried 99% of active markets and Polymarket 1%.
Deterministic · template v1 · 2026-06-28
As of 2026-06-28 · 00:00 UTC
Active Markets
219,824
00:00 UTC freeze
Open Interest
$2.36B
Kalshi OI + Polymarket liquidity
Markets Traded · 24h
12,785
with trading activity
Kalshi / Polymarket
99% / 1%
by active-market count
Domain Composition — 12 domains
Sports
164,444
Mixed / Multi-category
35,482
Other
11,752
Politics & Elections
3,726
Entertainment & Culture
2,261
Economics & Inflation
617
Crypto & Digital Assets
590
Companies & Business
326
Monetary Policy
280
Technology & AI
144
Climate & Weather
104
World & Geopolitics
67
Science & Health
31
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 = 219,824.
Largest Kalshi Series
Sports — multi-game parlays
154,903
Cross-category multi-markets
35,482
Music — artist streams
804
Midterm control
777
U.S. House races
606
Nextteamnba
363
NFL — next team moves
254
California primaries
239
Wcstageofelim
235
Primarymov
228
Wcmention
222
Wcteamleadgoal
219
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 June 28, 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 — June 28, 2026.” https://volroc.ai/prediction-markets/2026-06-28/
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