> ## 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).