Prints, sweeps, and blocks: reading the Kalshi tape.

Every print carries 4 facts: price, contract count, taker side, timestamp. It never carries a name, an account, a portfolio, or a motive. Kalshi's public feed is anonymous by design, and no endpoint reveals who traded. Everything a tape reader concludes is inference from shape, which is why honest tape tools state their thresholds and their uncertainty.

Consider one row: 1,200 contracts, YES side, 62 cents, 14:03:27. Notional is contracts times price, $744. The taker side says who paid for immediacy: someone wanted YES at 62 now rather than resting at 61 and waiting. What the print cannot say is whether the buyer was opening a view, closing a short, or hedging exposure held somewhere else.

A sweep is a rapid burst of same-side prints treated as one event, usually a single large order walking through the book and filling at successive price levels. Reading the burst as several traders is the most common way to misread it; it is one decision. Sweep events on Alerts show the combined notional and every constituent print. The full definition, thresholds included, and why the options-market meaning of "sweep" does not fit a single-book exchange, lives at what is a sweep.

A block trade is a large privately negotiated deal reported to the exchange outside the open book. Kalshi's API carries a block flag on every public trade, and measured from one full day of Kalshi's public tape, July 2026, it was true on 0 of 7.33 million trades, and on 0 of roughly 14 million rows examined in total. On Kalshi's public tape, blocks effectively do not print. Size arrives in the open book, as prints and sweeps, which is exactly what makes the tape worth watching, live at Alerts.