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

# Open Interest History

> Open-interest time series (with mark price and funding at each sample) — history the exchange does not offer.

Open interest is normally only visible as a live number on the [ticker](/perps/market-data/tickers). This endpoint gives you its history:

Each sample carries the mark price and funding rate at that moment, so OI-vs-price studies need no joins. Samples are minute-resolution, newest first.

| Parameter          | Description                           |
| ------------------ | ------------------------------------- |
| `after` / `before` | Time window (Unix seconds or ms)      |
| `limit`            | Max samples (default 500, up to 5000) |

The series accrues from July 9, 2026 onward. `/v3/perps/open-interest/{instrument}` is an alias of `/v3/perps/oi/{instrument}` — both forms work.


## OpenAPI

````yaml GET /v3/perps/oi/{instrument}
openapi: 3.1.0
info:
  title: PolyNode API
  description: >-
    Real-time Polymarket data API with decoded mempool settlements, OHLCV
    candles, and full Polygon JSON-RPC proxy.
  contact:
    name: PolyNode
    url: https://polynode.dev
  license:
    name: ''
  version: 2.0.0
servers:
  - url: https://api.polynode.dev
    description: Production
security:
  - api_key: []
paths:
  /v3/perps/oi/{instrument}:
    get:
      tags:
        - Perps
      summary: Open interest history
      description: >-
        Open-interest time series (with mark price and funding at each sample) —
        history the exchange does not offer.
      operationId: perps_oi
      parameters:
        - name: instrument
          in: path
          required: true
          description: Instrument id (e.g. `6`), symbol (`BTC-USD`), or bare asset (`btc`).
          schema:
            type: string
        - name: after
          in: query
          required: false
          description: Only rows after this time (Unix seconds or ms).
          schema:
            type: string
        - name: before
          in: query
          required: false
          description: Only rows before this time (Unix seconds or ms).
          schema:
            type: string
        - name: limit
          in: query
          required: false
          description: Max rows to return.
          schema:
            type: integer
      responses:
        '200':
          description: Success
          content:
            application/json:
              example:
                data:
                  - funding_rate: '0.0000125'
                    mark_price: '64125'
                    open_interest: '65.19026'
                    timestamp: 1783739407813
                  - funding_rate: '0.0000125'
                    mark_price: '64122'
                    open_interest: '65.19026'
                    timestamp: 1783739347801
                instrument_id: 6
                more: true
                symbol: BTC-USD
components:
  securitySchemes:
    api_key:
      type: apiKey
      in: header
      name: x-api-key

````