Guides / Platform
ProbSights whale tracking surfaces outsized Polymarket fills as they happen: notional size, side taken, which outcome token was bought, and when. Polymarket's markets are thin enough that a single large fill frequently sets the new price rather than trading against an existing one.
Because Polymarket settles on-chain, its fills carry a transaction_hash and the
fee_rate_bps actually applied. That means a whale fill is independently verifiable
— you can follow it on-chain rather than taking the feed's word for it, which is not possible
on Kalshi, where fills reconcile against a venue-issued trade_id instead. Fills
also reference an asset_id, the specific outcome token, which matters on
multi-outcome events where "bought $50k" is meaningless without knowing of what.
Polymarket size distribution varies enormously by series. A headline politics market absorbs
six figures without moving; a BTC 5-minute Up/Down contract does not. Set each tracked event's
whale_threshold_usd from that market's own avg_trade_size rather than
one global number — otherwise the crypto series is silent and the politics series is noise.
trade_size_usd against the market's avg_trade_size.transaction_hash.The public feed is previewable without an account. Per-event tracking with custom thresholds and webhook alerts is on the Builder plan. Add an event by ticker or by pasting its Polymarket URL.
Data from Kalshi and Polymarket. Search live API docs Pricing