layer
LIVEkalshi · polymarket

Match markets. Compare prices. Trade across venues.

Layer gives prediction-market developers one interface to find equivalent markets, compare live prices, execute trades, and track what actually happened.

01 matchFind the same event02 compareSee live prices03 costsKnow if it’s profitable04 tradePlace and cancel orders05 trackFills and positions06 testBacktest on history
01 matchLIVE

Match the same event across venues

Kalshi and Polymarket word the same event differently. Layer finds the equivalent markets so you don’t hand-map tickers to token IDs.

Semantic market matching
Kalshi + Polymarket
Different wording, same event
matched market · example
kalshiWill Bitcoin close above $150,000 on Dec 31?ticker · BTC_150K
polymarketBTC above $150K end of year?token_id · 0x7c3f…a91e
layerone matched market · mkt_btc_150k_dec31
02 compareLIVE

See the market in real time

Prices, spreads, and liquidity for matched markets, side by side. See which venue has the better trade.

Live pricesBest bid / askOrder booksWebSocket streams
market · yeskalshi bidkalshi askpoly bidpoly askgap
BTC above $150K by Dec 310.410.430.390.41+0.00
Fed cuts rates in December0.640.660.630.65-0.01
ETH above $5K by Dec 310.270.290.240.26+0.01
CPI above 3.0% in October0.510.530.500.52-0.01
One WebSocket for prices, order books, and fills. Same message format for both venues.illustrative prices · gap = best bid on one venue minus best ask on the other
ws · prices, books, fillslive
09:41:12.000pricekalshi BTC_150K bid 0.40 ask 0.42
09:41:13.241bookpolymarket ETH_5K yes 0.27 +1,200
09:41:14.482pricepolymarket BTC_150K bid 0.39 ask 0.41
09:41:15.723fillkalshi BTC_150K yes 100 @ 0.42
09:41:16.964bookkalshi BTC_150K yes 0.41 −300
09:41:17.205pricekalshi FED_DEC bid 0.62 ask 0.64
03 costsCOMING SOON

Know if the trade is worth it

A price gap isn’t profit. Layer shows fees and execution costs so you can tell whether an arbitrage is still positive after costs.

FeesSpreadsEstimated execution costsNet profitability
BTC above $150K · 100 contracts · example
buy yes · kalshi @ 0.42$42.00
buy no · polymarket @ 0.55$55.00
payout at resolution$100.00
gross gap+$3.00
kalshi fee−$1.71
polymarket fee−$0.00
est. slippage−$0.50
net+$0.79
illustrative · fees vary by venue and market
04 tradeLIVE

Execute through one interface

Same call to place or cancel an order on Kalshi or Polymarket. Change the venue, keep the code.

Place ordersCancel ordersCross-venue execution
pythoncopy
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# buy yes on kalshi, no on polymarket a = client.buy( venue="kalshi", market="mkt_btc_150k_dec31", side="yes", price=0.42, size=100 ) b = client.buy( venue="polymarket", market="mkt_btc_150k_dec31", side="no", price=0.55, size=100 ) # same cancel on either venue client.cancel(b.id) # same order shape back a.status # "filled" a.filled # 100 @ 0.42
05 trackLIVE

Know what actually happened

After an order is sent: what filled, what you hold, and where your money is, in one shape across venues.

Fills
Positions
BalancesCOMING SOON
P&LCOMING SOON
Resolution stateCOMING SOON
fillssame shape
kalshi · BTC_150K · yesfilled100 @ 0.42$42.00
polymarket · BTC_150K · nofilled100 @ 0.55$55.00
positionsone view
kalshi · BTC_150Kyes 100polymarket · BTC_150Kno 100
illustrative fills
06 testCOMING SOON

Test before you trade

Run strategies against historical prices and order books before risking real money.

Historical pricesCOMING SOON
Historical order booksCOMING SOON
Strategy researchCOMING SOON
BacktestingCOMING SOON
developer experience

One schema for both venues.

authOne API key
prices0.00–1.00 everywhere
ordersOne order model
sdkPython and TypeScript
CLICOMING SOON
WebhooksCOMING SOON
MCP · agent skillsCOMING SOON
roadmap

Prediction markets first. Built for automated trading across markets.

nowPrediction markets
LIVE
nextCrypto
COMING SOON
laterEquities
COMING SOON
laterTokenized assets
COMING SOON

Find the market. Trade the gap.

Matching, prices, execution, and fills for Kalshi and Polymarket, without rebuilding the plumbing.