Traders
Port strategies across exchanges and find an edge in the orderbooks.
The cross-exchange
prediction market API.
All exchanges. One event. Separate contracts, separate schemas, separate sides. Aggregated, normalized, and matched by Surface.
Kalshi + 
Polymarket| Kalshi series | Unique orderbooks | Settlement consistency |
|---|---|---|
| KXBTC15MBitcoin price up down | 7,493 | 97.5% |
| KXETH15METH 15M price up down | 7,493 | 97.7% |
| KXKBOGAMEKBO Game | 414 | 100.0% |
| KXMLBGAMEProfessional Baseball Game | 1,604 | 100.0% |
| KXMLBHRPro Baseball Home Runs | 22,371 | 100.0% |
| KXMLBKSPro Baseball Strikeouts | 5,237 | 100.0% |
| KXMLBTOTALPro Baseball Total Points | 5,365 | 100.0% |
Mapping mix
KXMLBHR 44.8%
KXBTC15M 15.0%
KXETH15M 15.0%
KXMLBTOTAL 10.7%
KXMLBKS 10.5%
KXMLBGAME 3.2%
KXKBOGAME 0.8%
Unique orderbooks49,977
Unique series7
Unique events18,169
Settlement consistency99.4%
Built for
Researchers
Unlock diverse market data and aggregate true probabilities.
Builders
Create seamless cross-exchange experiences for your users.
What it does
One call
Pass any Kalshi ticker or Polymarket slug and get the full normalized cluster.
Deterministic
Matches are determined ahead of time from explicit fields and rules.
Know your side
is_inverse tells you when YES on Kalshi equals NO on Polymarket.
More exchanges
Use one consistent API as Surface connects more prediction-market exchanges.
Match API — resolve any contract cross-exchangefull docs →
# resolve any contract cross-exchange
curl "https://surfaceapi.com/api/v1/match/KXMLBGAME-26MAR252005NYYSF-SF?include_rules=true" \
-H "X-API-Key: sk_surface_..."
# → 200 OK
{
"contracts": {
"kalshi": {
"KXMLBGAME-...-SF": { "question": "..." },
"KXMLBGAME-...-NYY": { "question": "..." }
},
"polymarket": {
"mlb-nyy-sf-2026-03-25": { "question": "..." }
}
},
"matches": {
"kalshi": {
"KXMLBGAME-...-SF": {
"polymarket": {
"mlb-nyy-sf-2026-03-25": { "is_inverse": false }
}
}
}
}
}