# Open interest by market | API reference | Femtos

> Every perp's open interest now, its 1 h / 24 h / 7 d change, totals per dex. GET /v1/hypercore/oi/markets on HyperCore: parameters, response fields and a live call per layer.

- Base URL: `https://api.femtos.xyz/v1` (REST) · `wss://api.femtos.xyz/v1/ws` (WebSocket) · MCP: `https://api.femtos.xyz/mcp`
- Auth: `Authorization: Bearer $FEMTOS_KEY`. Free key: https://dashboard.femtos.xyz/signup (browser), or with
  no browser: `GET https://femtos.xyz/accounts/agent/challenge`, solve its proof of work, then `POST https://femtos.xyz/accounts/agent/signup`
  (https://femtos.xyz/agents.md#agent-onboarding)
- Decimals are exact strings, times Unix milliseconds, addresses lowercase `0x`
- Whole API in one file: https://femtos.xyz/agents.md · OpenAPI: https://api.femtos.xyz/v1/openapi.json · Index: https://femtos.xyz/llms.txt
- Page with live calls: https://femtos.xyz/reference/open-interest-markets

## Open interest by market — GET `/v1/hypercore/oi/markets`

Every perp's open interest now, its 1 h / 24 h / 7 d change, totals per dex.

Layers: HyperCore. Not on Elysium or HyperEVM: the EVM layers trade on AMM pools, with no order book: pool detail and liquidity events cover a pool.
Page with live calls: https://femtos.xyz/reference/open-interest-markets?layer=hypercore

| Param | In | Example or values | Meaning |
|---|---|---|---|
| `dex` | query | (optional) | Only this perp dex ("" = the main one); every dex when absent |
| `sort` | query | `(empty)`, `usd`, `oi`, `pct24h`, `accounts` | Order, largest first (pct24h: largest increase first) |
| `limit` | query | `20` | Markets |

```bash
curl -H "Authorization: Bearer $FEMTOS_KEY" "https://api.femtos.xyz/v1/hypercore/oi/markets?sort=usd&limit=20"
```

| Field | Type | Meaning |
|---|---|---|
| `markets[]` | object | Ranked by `sort`: {coin, dex, oi, px, usd, longAccounts, shortAccounts, ago, pct} |
| `markets[].oi` | decimal | Open interest now (size) |
| `markets[].usd` | decimal \| null | oi × px (USD figure, 15 significant digits) |
| `markets[].pct` | object | Change of the size since then, as a fraction (0.05 = +5 %; 40 significant digits); null without a past value or from 0: {1h, 24h, 7d} |
| `dexes[]` | object | Largest first: {dex, usd, markets} |
| `totalUsd` | decimal | Σ usd of the markets listed (USD figure) |
| `asOf` | int \| null | End of the last minute computed (Unix ms) |

## Related (Liquidations & positions)

- [Liquidations](https://femtos.xyz/reference/liquidations.md) `GET /v1/liquidations`: Perp liquidations, newest first, one row per account, coin and block. (HyperCore)
- [Liquidations stream](https://femtos.xyz/reference/ws/liquidations.md) `WS hc.liquidations`: Each liquidation fill, the block it happens. One frame per block with all its matching events. (HyperCore)
- [Liquidation stats](https://femtos.xyz/reference/liquidation-stats.md) `GET /v1/liquidations/stats`: Totals, per coin, per time bucket and the largest, over a window. (HyperCore)
- [Liquidation stats stream](https://femtos.xyz/reference/ws/liquidation-stats.md) `WS hc.liquidations.stats`: The GET /v1/liquidations/stats answer (totals, per coin, per bucket, the largest), pushed on subscribe, then when a liquidation comes in (whole, or as a JSON Patch). (HyperCore)
- [Positions](https://femtos.xyz/reference/positions.md) `GET /v1/positions`: Open positions of one perp with leverage and liquidation price. (HyperCore)
- [Position changes](https://femtos.xyz/reference/ws/positions.md) `WS hc.positions`: Each perp position change, one per block, account and coin. One frame per block with all its matching events. (HyperCore)
- [Open positions stream](https://femtos.xyz/reference/ws/positions-open.md) `WS hc.positions.open`: The GET /v1/positions answer of one perp (size, entry, PnL, leverage, liquidation price), pushed on subscribe, then on each roll of the live positions (every 5 s) when it changes. (HyperCore)
- [Position change history](https://femtos.xyz/reference/position-changes.md) `GET /v1/positions/changes`: Past perp position changes of one coin over a size, one row per account and block. (HyperCore)
- [Open interest](https://femtos.xyz/reference/positions-overview.md) `GET /v1/positions/overview`: Open interest, accounts and unrealized PnL per perp. (HyperCore)
- [Open interest stream](https://femtos.xyz/reference/ws/positions-overview.md) `WS hc.positions.overview`: The GET /v1/positions/overview answer (long / short open interest, accounts, unrealized PnL per perp), pushed on subscribe, then on each roll of the live positions (every 5 s) when it changes (whole, or as a JSON Patch). (HyperCore)
- [Liquidation map](https://femtos.xyz/reference/liqmap.md) `GET /v1/positions/liqmap`: Notional that would be liquidated at each price around the mark. (HyperCore)
- [Liquidation levels stream](https://femtos.xyz/reference/ws/positions-liqmap.md) `WS hc.positions.liqmap`: The GET /v1/positions/liqmap answer of one perp (notional liquidated per price bucket), pushed on subscribe, then on each roll of the live positions (every 5 s) when it changes. (HyperCore)
- [Open interest history](https://femtos.xyz/reference/open-interest.md) `GET /v1/hypercore/oi`: Open interest bars of a perp since May 2023, after every block since March 2025: longs and shorts opened, closed, liquidated. (HyperCore)
- [Open interest per block](https://femtos.xyz/reference/ws/oi.md) `WS hc.oi`: The open interest of a perp after every block with a fill: longs and shorts opened, closed, liquidated. One frame per block with all its matching events. (HyperCore)
- [Open interest by position size](https://femtos.xyz/reference/open-interest-cohorts.md) `GET /v1/hypercore/oi/cohorts`: Long and short open interest of a perp by position size, every hour since September 2025. (HyperCore)
- [Who opened positions](https://femtos.xyz/reference/open-interest-opens.md) `GET /v1/hypercore/oi/opens`: The largest orders that opened longs or shorts on a perp in a window, with the account and whether it crossed the spread. (HyperCore)

Every page: https://femtos.xyz/reference.md