Odds API for Prediction Market Arbitrage

Compare Kalshi and Polymarket prices against Australian sportsbook odds in one schema. Find exchange-vs-book arbitrage in one odds API.

Kalshi and Polymarket prices sit in the same byBookmaker object as the Australian sportsbooks, keyed like any other book. That makes exchange-vs-book comparison a loop over one object rather than two integrations.

Why build your prediction market arbitrage on SockOdds

Exchanges and books together. polymarket, kalshi, betfairexchange, prophetexchange next to sportsbet.
Outcome alignment. Shared oddID.
No-vig benchmark. fairOdds.
Freshness per entry. available and lastUpdatedAt.
One schema. American string plus decimal on every entry.

How exchange-vs-sportsbook arbitrage works with our data

Pull exchange and book prices together

bookmakerID=polymarket,kalshi,sportsbet,tab.

Convert each price to implied probability

1 / decimal.

Benchmark against fairOdds

Flag the side where the book and the exchange disagree most.

Example request

curl "https://api.sockodds.com/v2/events/?leagueID=NFL&bookmakerID=polymarket,kalshi,sportsbet,pointsbet&oddID=points-home-game-ml-home&includeOpposingOdds=true&limit=1" \
  -H "x-api-key: YOUR_API_KEY"

Contract prices and book prices on the same outcome:

{
  "eventID": "afl_2026-09-03_fremantle_vs_hawthorn",
  "leagueID": "AFL",
  "odds": {
    "points-all-game-eo-odd": {
      "oddID": "points-all-game-eo-odd",
      "opposingOddID": "points-all-game-eo-even",
      "marketName": "Odd/Even Total Points",
      "statID": "points",
      "statEntityID": "all",
      "periodID": "game",
      "betTypeID": "eo",
      "sideID": "odd",
      "fairOdds": null,
      "bookOdds": "-116",
      "byBookmaker": {
        "unibet": {
          "odds": "-115",
          "decimal": 1.87,
          "available": true
        },
        "tabtouch": {
          "odds": "-118",
          "decimal": 1.85,
          "available": true
        }
      }
    }
  }
}

SockOdds vs building it yourself

Capability	SockOdds	building it yourself
Exchanges + books together	Same `byBookmaker` object	Separate exchange APIs plus an odds API
Outcome alignment	Shared `oddID`	Match by hand
No-vig benchmark	`fairOdds`	De-vig every book
Freshness	`available` + `lastUpdatedAt`	Track each source
Price normalisation	One schema	Map each source's format

Frequently asked questions

What is a prediction market arbitrage API?

A feed with contract prices and book prices on the same outcome, in one schema.

Does it include Kalshi and Polymarket?

Yes, where they price a covered fixture.

How do I compare exchange prices to sportsbook odds?

Convert both to implied probability.

Is exchange-vs-sportsbook arbitrage risk-free?

No — settlement rules differ and exchange liquidity is finite.

How is this different from sportsbook arbitrage?

The counterparty and the settlement terms.

How does this relate to the Prediction Market API?

Same feed, framed for arbitrage.

Related use cases

Odds API for Arbitrage Betting: An arbitrage betting API that returns every Australian book's price per market through byBookmaker, so you can scan every bookmaker and alt line for arbs and middles..
Odds API for Positive EV Betting: Positive EV betting API with no-vig fairOdds and every AU book's price side by side, so you can surface +EV bets without building your own devig pipeline..
Odds Comparison & Line Shopping API: Compare bookmaker odds with one API call.
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