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

# Get open interest



## OpenAPI

````yaml /api-spec/data-openapi.yaml get /oi
openapi: 3.0.3
info:
  title: Polymarket Data API
  version: 1.0.0
  description: >
    HTTP API for Polymarket data. This specification documents all public
    routes.
servers:
  - url: https://data-api.polymarket.com
    description: Relative server (same host)
security: []
tags:
  - name: Data API Status
    description: Data API health check
  - name: Core
  - name: Builders
  - name: Misc
paths:
  /oi:
    get:
      tags:
        - Misc
      summary: Get open interest
      parameters:
        - in: query
          name: market
          style: form
          explode: false
          schema:
            type: array
            items:
              $ref: '#/components/schemas/Hash64'
      responses:
        '200':
          description: Success
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/OpenInterest'
        '400':
          description: Bad Request
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '500':
          description: Server Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
components:
  schemas:
    Hash64:
      type: string
      description: 0x-prefixed 64-hex string
      pattern: ^0x[a-fA-F0-9]{64}$
      example: '0xdd22472e552920b8438158ea7238bfadfa4f736aa4cee91a6b86c39ead110917'
    OpenInterest:
      type: object
      properties:
        market:
          $ref: '#/components/schemas/Hash64'
        value:
          type: number
    ErrorResponse:
      type: object
      properties:
        error:
          type: string
      required:
        - error

````