Guides / Platform
In a market with $40,000 of resting depth, a single $25,000 fill is not one trade among many — it is most of the book. Prediction markets are thin enough that outsized flow moves the implied probability directly, which is why the large fills are worth isolating from the tape rather than reading the whole tape. That is what ProbSights whale tracking does across both venues at once.
A $10,000 fill is unremarkable in a headline election market and dominant in a 5-minute
crypto contract. A fixed dollar threshold therefore either floods you with noise on the deep
markets or shows nothing on the thin ones. The tracker gives each tracked event its own
whale_threshold_usd, and reports per-market avg_trade_size so you
can set that threshold from what the market actually does rather than by guessing.
| Field | Meaning |
|---|---|
trade_size_usd | Notional size — what makes it a whale |
price | Fill price, i.e. the implied probability paid |
taker_side | Which side lifted the book |
outcome | The outcome bought, on multi-outcome events |
platform | kalshi or polymarket |
event_title / market_title | Human-readable context |
event_ticker / market_ticker | Venue identifiers, for reconciliation |
timestamp | When it filled |
Size alone is not a signal. Three things make a large fill interesting:
trade_size_usd against the market's avg_trade_size, not against
other markets.A whale is also not automatically informed. Large fills include hedges, market-making inventory, and rolls between expiring contracts, none of which express a view. Treat the feed as a place to look, not a conclusion.
| Endpoint | Returns |
|---|---|
/v1/whales/public/feed | Cross-venue feed plus 24h volume, trade count, and average size |
/v1/whales/public/events | Events with whale activity, and 24h counts per event |
/v1/whales/markets | Markets ranked by 24h whale count |
/v1/whales/market/{id}/trades | Whale fills for one market |
/v1/whales/market/{id}/stats | Stats over 24h, 7d, or all |
/v1/whales/user/events | Your tracked events and their thresholds |
Filter any feed with min_trade_size and platform, and page with
limit/offset. Track an event by ticker or by pasting its Kalshi or
Polymarket URL — the tracker resolves the venue itself.
Set notify_on_whale_trade on a tracked event and register a
whale webhook; deliveries are
signed with a per-webhook secret. That is both faster and far cheaper against
rate limits than polling the feed
on a timer.
The public feed is previewable without an account, with a limited set of unlocked events. Per-event tracking with configurable thresholds and realtime alerts is on the Builder plan; Trader raises the tracked-event allowance and adds arbitrage webhooks.
Data from Kalshi and Polymarket. Search live API docs Pricing