Free Prediction Markets API
Top Polymarket markets by volume in the categories traders actually watch: Fed and rates, crypto, politics, macro. Current odds, 24-hour-ago odds, and a stored 15-minute history.
Endpoints
/api/markets/predictions?category=fed-rates|crypto|politics|macroActive markets by volume with current and 24h-ago odds.
/api/markets/predictions/csvRaw 15-minute odds history as CSV, up to 50,000 rows.
Example
curl "https://xoomar.com/api/markets/predictions?category=fed-rates"
Response Shape
Every endpoint returns the same JSON envelope: { data, updatedAt, source, docs }. The data field is an array of records with these fields:
| Field | Type | Description |
|---|---|---|
| pmId | string | Polymarket market id |
| question | string | Market question |
| category | string | fed-rates, crypto, politics, macro, other |
| volumeUsd | string | null | Lifetime traded volume |
| odds | array | Latest outcome prices, e.g. [{outcome: 'Yes', price: '0.32'}] |
| odds24hAgo | array | Prices ~24 hours earlier for change computation |
Prices are probabilities in 0-1. Categories come from question-text classification; the odd big market outside these categories appears under other.
Numeric values arrive as strings where precision matters (prices, rates); parse with your language's decimal type for accounting-grade math. Rate limiting is fair-use per IP; a 429 response includes a Retry-After header. No authentication or API key needed. Attribution is appreciated: xoomar.com/markets.
Need more headroom? A free account raises your limit to 120 requests a minute with an X-API-Key header.
Frequently Asked Questions
Why not just use the Polymarket API directly?
How fresh are the odds?
Which markets are tracked?
Is historical data available?
Data on this page is provided for informational purposes only and is not financial advice. See our editorial policy.