# Missing API key

Resolve missing API key errors.

The `X-Api-Key` header is absent or empty.

Server-side requests must include a valid [API key](/explanation/application/api-keys) through the `X-Api-Key` header.

## Response

All error responses follow the [Problem Details (RFC 9457)](/reference/api/overview#errors) format. The `type`, `title`, `status`, and `detail` fields are always present, while `instance` may be omitted depending on the API.

Here is an example of the response returned for this error:

```json
{
  "type": "https://croct.help/api/authentication/missing-api-key",
  "title": "The API key is missing.",
  "status": 401,
  "detail": "The request must include an API key, but none was provided.",
  "instance": "/client/web/content"
}
```