API reference

Spreads: cross-venue price gaps

Where the same outcome is cheaper to buy on one venue than it sells for on the other, largest gap first. Built from executable bid and ask.

A lead, not guaranteed arbitrage

Gaps are gross

A gap is the sell bid on one venue minus the buy ask on the other. It ignores trading fees, withdrawal costs and how much size the order books can fill. Settlement rules can differ between venues too. Treat every gap as a lead to check, not money on the table.

By default (parity=reviewed) you only get outcomes whose settlement rules a person checked match. parity=any adds every matched outcome; rules may differ.
price_state is actionable, indicative or stale. Only actionable gaps use current executable prices on both venues.

GET/api/public/v1/spreadsAPI key required

List spreads

Largest gaps first. Returns pagination: null.

Parameters

Name	In	Type	Required	Default	Description
event	query	string	No	—	Only this event slug.
min_gap	query	number	No	0.02	Minimum gap in probability points, 0 to 1. `0.02` = 2 points.
min_volume	query	number	No	1000	Minimum volume in US dollars on each venue.
parity	query	"reviewed" \| "any"	No	reviewed	`reviewed`: only outcomes whose rules a person checked match. `any`: every matched outcome.
limit	query	integer	No	50	Rows, 1 to 200.

Request

curl -s 'https://api.thepredictionmarkets.com/api/public/v1/spreads?min_gap=0.02&limit=5' \
  -H 'X-API-Key: tpm_demo_key_authorized_2026'

Response

Example 200 response. Values are illustrative and change over time.

200 OK

{
  "data": [
    {
      "event_slug": "democratic-presidential-nominee-2028",
      "event_title": "Democratic Presidential Nominee 2028",
      "outcome_key": "candidate:acor",
      "outcome_title": "Alexandria Ocasio-Cortez",
      "gap": 0.024,
      "buy": {
        "venue": "kalshi",
        "price": 0.14
      },
      "sell": {
        "venue": "polymarket",
        "price": 0.164
      },
      "quote_basis": "executable_bid_ask",
      "price_state": "actionable",
      "quote_age_seconds": 4,
      "match_quality": "auto_high"
    }
  ],
  "pagination": null
}

Response fields

Field	Type	Description
event_slug, event_title	string	The event.
outcome_key, outcome_title	string	The matched outcome.
gap	number	Gross gap in probability points: `sell.price - buy.price`.
buy	{venue, price}	Where Yes is cheapest to buy (its ask).
sell	{venue, price}	Where Yes sells highest (its bid).
quote_basis	string \| null	`executable_bid_ask` when both legs are live bid/ask.
price_state	string \| null	`actionable`, `indicative` or `stale`.
quote_age_seconds	integer \| null	Age of the quotes behind the gap.
match_quality	string \| null	How confident the outcome match is, e.g. `auto_high`.

Errors

HTTP	Code	When
400	validation.invalid_parameter	A filter is out of range, e.g. `min_gap=2`.
401	auth.missing_key	No `X-API-Key` header was sent.
401	auth.invalid_key	The key is wrong or was revoked.
429	rate_limit.per_second	Too many requests this second. Wait for `Retry-After`.

400 validation.invalid_parameter

{
  "error": {
    "code": "validation.invalid_parameter",
    "message": "min_gap: Input should be less than or equal to 1",
    "request_id": "0f8969a6-0968-4d7c-9cbb-de379e8c19c4"
  }
}

All codes are listed on the errors page.

Try it

Runs a live request from your browser. Pre-filled with the shared demo key (5 requests per second for everyone); paste your own key for steadier results.

Request URLX-API-Keyeventquerymin_gapquerymin_volumequeryparityquerylimitquery

HTTP: —Time: —Rows: —Remaining this second: —Request: —

Press Send to run this request.

Build with TPM

Get your free API key

One key gives you Kalshi and Polymarket events, prices with freshness, price history, cross-venue gaps and the live quotes WebSocket.

Get a free API key Read the quickstart