How do I access Polymarket & Kalshi market data?

Over a metered REST API (one Bearer key, keyset pagination) for history and latest snapshots, and a live WebSocket stream for the present — both emitting the identical JSON. The free Explorer tier needs no card to start; paid plans widen the history window and rate limits. Full reference and copy-pasteable examples live in the docs.

Can I backtest Polymarket & Kalshi strategies with this data?

Yes — that's what it's for. You get the full historical order book to replay a market and size fills against the liquidity that was actually there, then run the backtest in your own stack. Because history and the live stream share one JSON format, the code you backtest with also trades live.

Can I cancel anytime?

Yes. Paid plans are month to month and the free Explorer tier needs no card to start. Cancel anytime from the dashboard.

Polymarket & Kalshi market data

Polymarket & Kalshi Market Data

Most "prediction-market market data" you can buy is a last price sampled on a clock — a single number that hides the spread and the size behind it. DepthFeed serves the real thing: the full order book, the market's own price, and the underlying crypto price, on every snapshot, over one API.

Polymarket & Kalshi market data, done properly, is three series on one timeline: the full order book (the full bid/ask ladder on both sides, every level (up to 100 per side on Kalshi)), the market's own 0–1 price (its implied probability), and the underlying crypto reference price. DepthFeed records event-driven websocket capture on Polymarket and Limitless, and continuous full-depth polling on Kalshi and stamps all three on every snapshot with epoch-millis timestamps, over a REST API and a live WebSocket.

Polymarket & Kalshi market data at a glance

Venues: Polymarket · Kalshi · Limitless
Capture: Event-driven WS (Poly) · full-depth poll (Kalshi)
Live latency: Polymarket ~10 ms median (measured)
Depth: Full ladder, both sides (≤100 levels Kalshi)
Assets: 7 — BTC · ETH · SOL · XRP · DOGE · BNB · HYPE
Timestamps: Epoch-ms exchange + receive, per snapshot
Underlying price: Binance spot/futures, joined per snapshot
History: 7/30/90-day windows + full archive (Desk)
Delivery: REST API + live WebSocket, identical JSON
Resolution: Every change, or ?interval= 30s–1d downsample

What Polymarket & Kalshi market data covers

The full book, price, and underlying — one snapshot

Each snapshot carries the full bid/ask ladder on both sides, every level (up to 100 per side on Kalshi), the market's live 0–1 price read from that book, and the ASOF-joined Binance price for the underlying (BTC, ETH, SOL, XRP, DOGE, BNB, and HYPE) — all on one epoch-millis timeline. You reconstruct spread, depth, and the spot move that repriced the contract from a single feed, not three stitched-together sources.

Depth, not a last price

A last-price feed can't tell you whether your order would have filled or what slippage it would have paid. Because DepthFeed captures every book change on Polymarket (~10 ms median live delivery, measured) and the full Kalshi depth roughly every 1.5 seconds, the polymarket & kalshi market data you replay is the book that actually existed at each change — the columns a realistic backtest is built on.

Four views, one schema

The same market data drives every surface: the cross-venue order book, the price series, the historical archive, and the API. Pull whichever you need in the identical JSON — start with the Polymarket & Kalshi order book, price data, historical archive, or data API below.

Start pulling polymarket & kalshi market data

Free Explorer tier, no card. Full bid/ask depth and the underlying price on every snapshot, over a REST API and a live WebSocket stream.

Start free — no card Read the API docs

Questions, answered.

Three layers on every snapshot: the full order book (bid/ask price and size on both sides, up to 100 levels per side on Kalshi), the market's own 0–1 price (implied probability, read from that book), and the underlying crypto reference price — each stamped with epoch-millis exchange and receive timestamps. Not a single sampled last price.