---
search:
  tags:
    - Markets
    - GET
seo:
  description: >-
    Returns the current aggregated order book for each requested market, ordered
    by ticker ascending. Reference for the GET /orderbooks endpoint in the REST
    API.
sidebar:
  label: List Order Books
  badge: GET
title: List Order Books
type: openapi-operation
---
Returns the current aggregated order book for each requested market, ordered by ticker ascending.

### Endpoint

- Method and path: `GET /orderbooks`
- Operation ID: `listOrderbooks`
- API reference: [GET /orderbooks](/api-reference/rest/markets/list-orderbooks)
- Complete specification: [OpenAPI (YAML)](/openapi.yml)
- Spec location (JSON Pointer): `#/paths/~1orderbooks/get`

#### Authorization

- Credential: optional. An authenticated request is metered against the member's read bucket and returns RateLimit headers; an unauthenticated request shares the public per-client limit.
- Accepted credentials: `UDX-Access-Key` header and `UDX-Access-Timestamp` header and `UDX-Access-Signature` header; or Bearer token in `Authorization`
- Details: [Authentication](/reference/authentication)

#### Parameters

```yaml
- $ref: "#/components/parameters/VersionHeader"
- name: ticker
  in: query
  required: true
  description: The markets to read. Repeat the parameter for each ticker. Tickers that don't name a market are ignored.
  style: form
  explode: true
  schema:
    type: array
    minItems: 1
    maxItems: 25
    items:
      $ref: "#/components/schemas/Ticker"
  example:
    - UDX-EXAMPLE-MARKET
    - UDX-EXAMPLE-MARKET-B
- name: depth
  in: query
  required: false
  description: Maximum number of price levels to return per side of each book.
  schema:
    type: integer
    format: int32
    minimum: 1
    maximum: 1000
    description: Levels per side.
    example: 1
```


#### Responses

##### `200`

The aggregated order books.

Headers:

```yaml
UDX-Version:
  $ref: "#/components/headers/VersionHeader"
Cache-Control:
  $ref: "#/components/headers/NoStore"
```

Content type: `application/json`

Schema:

```yaml
$ref: "#/components/schemas/OrderbooksResponse"
```

Example: Example

```json
{
  "orderbooks": [
    {
      "ticker": "UDX-EXAMPLE-MARKET",
      "bids": [
        [
          "0.54",
          "120"
        ]
      ],
      "asks": [
        [
          "0.56",
          "80"
        ]
      ]
    },
    {
      "ticker": "UDX-EXAMPLE-MARKET-B",
      "bids": [],
      "asks": [
        [
          "0.31",
          "45"
        ]
      ]
    }
  ]
}
```

##### `400`

The request doesn't conform to this spec.

Headers:

```yaml
UDX-Version:
  $ref: "#/components/headers/VersionHeader"
```

Content type: `application/problem+json`

Schema:

```yaml
$ref: "#/components/schemas/ProblemDetails"
```

Example: Invalid request parameters

```json
{
  "type": "urn:udx:problem:invalid-request-parameters",
  "title": "Bad Request",
  "status": 400,
  "detail": "invalid request parameters",
  "instance": "urn:request-id:8f14e45f-ceea-4abc-a743-e89a34d3f6ef"
}
```

Example: Unknown UDX-Version

```json
{
  "type": "urn:udx:problem:unknown-version",
  "title": "Bad Request",
  "status": 400,
  "detail": "unknown UDX-Version \"1999-01-01\"; supported versions: 2026-07-15",
  "instance": "urn:request-id:8f14e45f-ceea-4abc-a743-e89a34d3f6ef"
}
```

##### `429`

The request rate was exceeded. An unauthenticated request shares the public per-client limit; an authenticated request is metered against the member's read bucket.

Headers:

```yaml
UDX-Version:
  $ref: "#/components/headers/VersionHeader"
Retry-After:
  $ref: "#/components/headers/RetryAfter"
Cache-Control:
  $ref: "#/components/headers/NoStore"
```

Content type: `application/problem+json`

Schema:

```yaml
$ref: "#/components/schemas/ProblemDetails"
```

Example: Public limit exceeded

```json
{
  "type": "urn:udx:problem:unauthenticated-rate-limit-exceeded",
  "title": "Too Many Requests",
  "status": 429,
  "detail": "this client has temporarily exceeded the public request rate",
  "instance": "urn:request-id:8f14e45f-ceea-4abc-a743-e89a34d3f6ef"
}
```

Example: Member limit exceeded

```json
{
  "type": "urn:udx:problem:member-rate-limit-exceeded",
  "title": "Too Many Requests",
  "status": 429,
  "detail": "this member has temporarily exceeded its request rate",
  "instance": "urn:request-id:8f14e45f-ceea-4abc-a743-e89a34d3f6ef"
}
```

##### `500`

Something went wrong on UDX's side.

Headers:

```yaml
UDX-Version:
  $ref: "#/components/headers/VersionHeader"
```

Content type: `application/problem+json`

Schema:

```yaml
$ref: "#/components/schemas/ProblemDetails"
```

Example: Internal server error

```json
{
  "type": "urn:udx:problem:internal-error",
  "title": "Internal Server Error",
  "status": 500,
  "detail": "internal error",
  "instance": "urn:request-id:8f14e45f-ceea-4abc-a743-e89a34d3f6ef"
}
```

##### `503`

Request admission is unavailable.

Headers:

```yaml
UDX-Version:
  $ref: "#/components/headers/VersionHeader"
Cache-Control:
  $ref: "#/components/headers/NoStore"
```

Content type: `application/problem+json`

Schema:

```yaml
$ref: "#/components/schemas/ProblemDetails"
```

Example: Admission temporarily unavailable

```json
{
  "type": "urn:udx:problem:request-admission-unavailable",
  "title": "Service Unavailable",
  "status": 503,
  "detail": "request admission is temporarily unavailable",
  "instance": "urn:request-id:8f14e45f-ceea-4abc-a743-e89a34d3f6ef"
}
```


#### Referenced definitions

The references in the excerpts above resolve to these definitions in the complete specification.

##### `#/components/headers/VersionHeader`

```yaml
description: API version used for this response.
schema:
  type: string
  maxLength: 10
  description: A dated API version (YYYY-MM-DD).
  example: 2026-07-15
```

##### `#/components/headers/NoStore`

```yaml
description: Prevents caching this response.
schema:
  type: string
  enum:
    - no-store
  description: Always the cache directive no-store.
  example: no-store
```

##### `#/components/schemas/OrderbooksResponse`

```yaml
type: object
description: The aggregated order books for the requested markets.
required:
  - orderbooks
properties:
  orderbooks:
    type: array
    maxItems: 25
    description: One order book per requested market, ordered by ticker ascending. A market with no visible orders has empty bids and asks.
    items:
      $ref: "#/components/schemas/Orderbook"
```

##### `#/components/schemas/Orderbook`

```yaml
type: object
description: The aggregated order book for a market.
required:
  - ticker
  - bids
  - asks
properties:
  ticker:
    $ref: "#/components/schemas/Ticker"
  bids:
    type: array
    maxItems: 1000
    description: Bid levels, best first, as [price, quantity] pairs in YES dollars.
    items:
      $ref: "#/components/schemas/PriceLevel"
  asks:
    type: array
    maxItems: 1000
    description: Ask levels, best first, as [price, quantity] pairs in YES dollars.
    items:
      $ref: "#/components/schemas/PriceLevel"
```

##### `#/components/schemas/Ticker`

```yaml
type: string
minLength: 1
maxLength: 128
description: A human-meaningful natural key naming a single-leg or multi-leg market.
example: UDX-EXAMPLE-MARKET
```

##### `#/components/schemas/PriceLevel`

```yaml
type: array
description: A single aggregated book level as a two-element [price, quantity] pair.
minItems: 2
maxItems: 2
items:
  type: string
  maxLength: 24
  description: A fixed-point decimal string (price in dollars, or quantity in contracts).
```

##### `#/components/schemas/ProblemDetails`

```yaml
type: object
description: An RFC 9457 machine-readable error, returned on every non-2xx response. The response's Content-Language header identifies the language used by title and detail, and Vary includes Accept-Language.
required:
  - type
  - title
  - status
properties:
  type:
    type: string
    format: uri-reference
    maxLength: 2048
    description: A stable URN identifying the kind of problem, for example urn:udx:problem:insufficient-permissions. Branch on it rather than on the localized detail. It is an identifier, not a URL to dereference.
  title:
    type: string
    maxLength: 40
    example: Bad Request
    description: A localized, human-readable summary of the error category. Stable for a given status code and resolved language — clients must not use it as a machine-readable discriminator.
  status:
    type: integer
    example: 400
    description: The HTTP status code, repeated from the response itself.
  detail:
    type: string
    maxLength: 500
    example: malformed request body
    description: A localized, human-readable explanation specific to this occurrence. Clients must not parse it for machine-readable information.
  instance:
    type: string
    format: uri-reference
    maxLength: 100
    example: urn:request-id:8f14e45f-ceea-4abc-a743-e89a34d3f6ef
    description: An identifier for this specific occurrence, so it can be correlated with server-side logs if you need to report it.
```

##### `#/components/headers/RetryAfter`

```yaml
description: Whole seconds to wait before retrying.
schema:
  type: integer
  minimum: 1
  description: A positive delay in whole seconds.
  example: 2
```

##### `#/components/parameters/VersionHeader`

```yaml
name: UDX-Version
in: header
required: false
description: Dated API version (YYYY-MM-DD).
schema:
  type: string
  minLength: 10
  maxLength: 10
  description: A dated API version (YYYY-MM-DD).
  example: 2026-07-15
```