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Free Prediction Market API: Real-Time Odds, Volume & Liquidity Data

Updated March 2026 — A free, public JSON API for prediction market data. No API key required. Get real-time odds from Polymarket and more in seconds.

curl https://predscope.com/api/markets.json

API Endpoint

Response Format

The API returns a JSON object with a meta object and a markets array. Each market object contains pricing, volume, and outcome data.

Top-Level Structure

{
  "meta": { ... },
  "markets": [
    {
      "title": "2026 FIFA World Cup Winner",
      "slug": "2026-fifa-world-cup-winner-595",
      "url": "/event/2026-fifa-world-cup-winner-595",
      "volume": 432222665.75,
      "volume_24h": 16333352.32,
      "liquidity": 49475505.55,
      "categories": ["sports"],
      "outcomes": [
        {
          "title": "Spain",
          "probability": 0.1565,
          "day_change": 0.001
        },
        {
          "title": "Argentina",
          "probability": 0.1420,
          "day_change": -0.003
        }
      ]
    },
    ...
  ]
}

Market Object Fields

Outcome Object Fields

Code Examples

Copy-paste these examples to start pulling prediction market data in seconds.

# Fetch all prediction markets
curl -s https://predscope.com/api/markets.json | head -c 500

# Pretty-print with jq
curl -s https://predscope.com/api/markets.json | jq '.markets[:3]'

# Get only politics markets
curl -s https://predscope.com/api/markets.json | \
  jq '[.markets[] | select(.categories[] == "politics")]'

# Get markets sorted by 24h volume
curl -s https://predscope.com/api/markets.json | \
  jq '[.markets | sort_by(-.volume_24h)[:10] | .[] | {title, volume_24h}]'

import requests

# Fetch all markets
response = requests.get("https://predscope.com/api/markets.json")
data = response.json()

markets = data["markets"]
print(f"Total markets: {len(markets)}")

# Find the top 5 markets by 24h volume
top_markets = sorted(markets, key=lambda m: m["volume_24h"], reverse=True)[:5]

for market in top_markets:
    print(f"\n{market['title']}")
    print(f"  24h Volume: ${market['volume_24h']:,.0f}")
    print(f"  Liquidity:  ${market['liquidity']:,.0f}")
    for outcome in market["outcomes"][:3]:
        pct = outcome["probability"] * 100
        chg = outcome["day_change"] * 100
        print(f"  {outcome['title']}: {pct:.1f}% ({chg:+.1f}%)")


# Filter by category
politics = [m for m in markets if "politics" in m["categories"]]
crypto = [m for m in markets if "crypto" in m["categories"]]
sports = [m for m in markets if "sports" in m["categories"]]

print(f"\nPolitics: {len(politics)} | Crypto: {len(crypto)} | Sports: {len(sports)}")

// Fetch prediction market data (Node.js or browser)
async function getMarkets() {
  const res = await fetch("https://predscope.com/api/markets.json");
  const data = await res.json();
  return data.markets;
}

// Example: Display top movers (biggest 24h changes)
async function topMovers() {
  const markets = await getMarkets();

  // Flatten all outcomes with their market context
  const outcomes = markets.flatMap(m =>
    m.outcomes.map(o => ({
      market: m.title,
      outcome: o.title,
      probability: o.probability,
      dayChange: o.day_change
    }))
  );

  // Sort by absolute day change
  outcomes.sort((a, b) => Math.abs(b.dayChange) - Math.abs(a.dayChange));

  console.log("Top 10 Movers (24h):");
  outcomes.slice(0, 10).forEach(o => {
    const pct = (o.probability * 100).toFixed(1);
    const chg = (o.dayChange * 100).toFixed(1);
    console.log(`  ${o.outcome} (${o.market}): ${pct}% (${chg > 0 ? "+" : ""}${chg}%)`);
  });
}

topMovers();


// Example: Poll for updates every 5 minutes
setInterval(async () => {
  const markets = await getMarkets();
  console.log(`[${new Date().toISOString()}] ${markets.length} markets loaded`);
}, 5 * 60 * 1000);

Use Cases

The PredScope API is used by developers, researchers, and traders to build tools on top of prediction market data. Here are the most common applications:

API Comparison: PredScope vs Polymarket vs Kalshi

How does the PredScope API compare to the official prediction market platform APIs?

When to use PredScope: You want to read prediction market odds and data quickly without any setup. Ideal for dashboards, bots, research, and price tracking.

When to use official APIs: You need to place trades programmatically, access full order book depth, or build a trading bot that executes on a specific platform. You will need the Polymarket or Kalshi API for that.

Rate Limits & Fair Use

The API is free and open, but we ask that you follow these guidelines to keep it available for everyone:

If you exceed the rate limit, you will receive a 429 Too Many Requests response. Wait a few minutes and retry. There is no penalty or ban for occasional overages.

Tips & Best Practices

• Cache locally. Data updates every 5 minutes. Polling more frequently wastes your rate limit and returns identical data.
• Use volume_24h for sorting. This surfaces the most actively traded markets. Markets with high 24h volume are where the action is.
• Filter by category. Use the categories array to show only markets in your area of interest (politics, crypto, sports, etc.).
• Watch day_change for signals. A large day_change value often indicates breaking news or a major shift in sentiment. Great for alert bots.
• Combine with other data. Merge prediction market probabilities with polling data, financial data, or social media signals for richer analysis.
• Credit PredScope. If you use the API in a project, we appreciate a link back to predscope.com.

Frequently Asked Questions

Related Guides

• What Are Prediction Markets? — Introduction for beginners
• Prediction Market Arbitrage — Cross-platform profit strategies
• How to Trade on Polymarket — Step-by-step trading guide
• Polymarket Review 2026 — Full platform review
• Kalshi Review 2026 — Alternative platform review
• Crypto Prediction Markets — BTC, ETH, and crypto trading
• Prediction Market Accuracy — How accurate are the odds?
• Best Prediction Markets 2026 — All platforms ranked
• Polymarket vs Kalshi — Detailed comparison
• Prediction Market Glossary — Key terms explained

See also: Kalshi API — learn more about Kalshi API.