> ## Documentation Index
> Fetch the complete documentation index at: https://artemis.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Prediction Markets

> Volume, open interest, active markets and category splits for event-contract venues

Artemis tracks prediction markets (event-contract venues where users trade binary outcomes that settle to \$1 if an event resolves true and \$0 otherwise) on the same framework as exchanges: daily volume, open interest, transactions, and active users. On-chain venues are indexed from raw fills; centralized venues come from each exchange's official settlement feed. For per-venue data sources and full methodology, see [Prediction Markets](/docs/prediction-markets/overview).

## Metrics

| Metric | Label | Unit | Aggregation |
| - | - | - | - |
| `SPOT_VOLUME` | Spot Volume | Currency | `SUM` |
| `OPEN_INTEREST` | Open Interest | Currency | `LAST` |
| `SPOT_TXNS` | Spot DEX Transactions | Nominal | `SUM` |
| `SPOT_DAU` | Spot DEX Daily Active Users | Nominal | `AVERAGE` |
| `MAU` | Monthly Active Addresses | Nominal | `AVERAGE` |
| `FEES` | Fees | Currency | `SUM` |
| `TVL` | Total Value Locked | Currency | `LAST` |
| `ACTIVE_MARKETS` | Active Markets | Nominal | `LAST` |
| `PM_UTILITY_RATIO` | PM Utility Ratio | Nominal | `AVERAGE` |
| `SPOT_VOLUME_SPORTS` | Spot Volume (Sports) | Currency | `SUM` |
| `SPOT_VOLUME_POLITICS` | Spot Volume (Politics) | Currency | `SUM` |
| `SPOT_VOLUME_CRYPTO` | Spot Volume (Crypto) | Currency | `SUM` |
| `SPOT_VOLUME_WITHOUT_SPORTS` | Prediction Market Spot Volume Without Sports | Currency | `SUM` |
| `OPEN_INTEREST_WITHOUT_SPORTS` | Open Interest Without Sports | Currency | `LAST` |
| `MAKER_REBATES` | Maker Rebates | Currency | `SUM` |
| `COMBO_VOLUME` | Combo Volume | Currency | `SUM` |

Not every venue exposes every metric: `MAKER_REBATES` and `COMBO_VOLUME` are venue-specific, and the category splits are populated for the largest venues. `TVL` is the collateral a venue custodies on-chain, so it exists only for on-chain venues: Polymarket reported \$326.1M and Opinion \$3.7M on 2026-08-01, while the centralized venues return no value. Check with [`GET /supported-metrics/`](/docs/artemis-api/discovery).

## Covered venues

| Symbol | Venue |
| - | - |
| `kalshi` | Kalshi |
| `polymarket` | Polymarket |
| `cme` | CME |
| `nadex` | Nadex |
| `forecastex` | ForecastEx |
| `gemini` | Gemini |
| `rothera` | Rothera |
| `opinion` | Opinion |
| `limitless` | Limitless |
| `predict` | Predictdotfun |
| `hip4` | HIP-4 |

All 11 venues above return `SPOT_VOLUME`.

## Reading volume across venues

<Warning>
  On most venues event contracts are **\$1-face binaries**, so a traded-contract count equals USD notional, directly comparable across Kalshi, Polymarket, ForecastEx, Gemini, Rothera and HIP-4.

  **Nadex and CME are the exception.** Their contract faces vary by product family, so `SPOT_VOLUME` is a raw contract count that does not convert to USD and must not be compared 1:1 with the \$1-face venues.

  `SPOT_VOLUME` is **notional**, not the price-weighted premium actually traded (roughly half of notional at typical prices).

  Perpetual futures on Kalshi and Polymarket are USD-native and live in separate `PERP_VOLUME` / `PERP_OPEN_INTEREST` fields. Never add them to event-contract `SPOT_VOLUME`.
</Warning>

## Example: Volume and open interest

```bash theme={null}
curl -s "https://data-svc.artemisxyz.com/v2/data/SPOT_VOLUME,OPEN_INTEREST?symbols=kalshi,polymarket,nadex,opinion,rothera&startDate=2026-07-25&endDate=2026-08-01&summarize=true&APIKey=$ARTEMIS_API_KEY"
```

| Venue | Volume | Open interest |
| - | - | - |
| Kalshi | \$1,383.7M | \$700.3M |
| Polymarket | \$300.3M | \$402.3M |
| Nadex | 37.5M contracts | 17.0M contracts |
| Opinion | \$25.8M | \$3.7M |
| Rothera | \$4.6M | \$10.4M |

Nadex is shown in contracts rather than dollars, per the caveat above.

## Split volume by category

Kalshi and Polymarket carry a cross-venue-comparable category taxonomy:

```bash theme={null}
curl -s "https://data-svc.artemisxyz.com/v2/data/SPOT_VOLUME?symbols=kalshi&startDate=2026-08-01&endDate=2026-08-01&dimensionType=CATEGORY&APIKey=$ARTEMIS_API_KEY"
```

Kalshi's 2026-08-01 volume across 17 categories, top six:

| Category | Volume |
| - | - |
| Sports | \$1,067.0M |
| Crypto | \$191.0M |
| Exotics | \$95.4M |
| Other | \$16.8M |
| Climate and Weather | \$3.1M |
| Elections | \$3.1M |

Sports is 77% of the day's volume. The same cut works on `OPEN_INTEREST`.

For a fuller walkthrough see [Prediction markets recipe](/docs/artemis-api/recipes/prediction-markets).


This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.