> ## Documentation Index
> Fetch the complete documentation index at: https://docs.neural4d.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Common headers

> Authentication and request tracing headers shared by API v1 endpoints.

## Authorization

Send your API key with the Bearer scheme on every request.

```http theme={null}
Authorization: Bearer ${YOUR_API_KEY}
```

## X-Request-Id

`X-Request-Id` is optional and correlates client logs with Neural4D logs. When you send a valid value, the service uses it unchanged and returns the same value in the response header. If the header is omitted or invalid, the service generates a new value and returns it in the response header.

The value must contain `1-128` ASCII characters. It may contain only letters (`A-Z`, `a-z`), digits (`0-9`), periods (`.`), underscores (`_`), and hyphens (`-`). Examples include `client-request-123` and `order_20260804.1`.

```http theme={null}
X-Request-Id: client-request-123
```

| Header          | Direction            | Description                                                                                           |
| --------------- | -------------------- | ----------------------------------------------------------------------------------------------------- |
| `Authorization` | Request              | Required API key using the Bearer scheme.                                                             |
| `X-Request-Id`  | Request and response | Optional request ID; a valid client value is returned unchanged, otherwise the service generates one. |