# Headers

API requests and responses must use specific headers to comply with the JSON API specification.
These headers define the content type, accepted formats, and authentication requirements.

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## Client responsibilities

Clients must include the following headers in requests:

- `Content-Type: application/vnd.api+json` - Required for all requests that send JSON API data. Do **not** include media type parameters.

If these headers are not correctly set, the server may reject the request.

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## Server responsibilities

Servers must include the following headers in responses:

- `Content-Type: application/vnd.api+json` - All responses containing JSON API data must use this header without media type parameters.

Servers return the following errors if headers are invalid:

- **415 Unsupported Media Type** - Returned if the request contains a `Content-Type` header with invalid parameters.
- **406 Not Acceptable** - Returned if the request's `Accept` header specifies JSON API but modifies it with parameters.

Refer to the [JSON API specification](https://jsonapi.org/format/#content-negotiation) for detailed content negotiation
rules.

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## Required headers

The table below lists the required headers for all API requests:

| **Header** | **Optional** | **Description** |
| --- | --- | --- |
| `Accept` | No | Must be `application/vnd.api+json`. |
| `Content-Type` | No | Must be `application/vnd.api+json`. |
| `Api-Key` | No | [Authorization Header](../configuration.html#api-key) used for authentication. |

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