> For the complete documentation index, see [llms.txt](https://developers.mobile-text-alerts.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.mobile-text-alerts.com/api-basics/request-response-headers.md).

# Request / Response Headers

Learn which headers are used in Mobile Text Alerts API calls and responses.

## Request Headers

Request headers contain information about the client request. These are the header types used by the Mobile Text Alerts API.

### Authorization

The Authorization header is used for authentication in HTTP requests. It contains a token or credentials used to prove the client's identity. The Mobile Text Alerts API uses bearer token authentication with an API key.

**Header structure:** `"Authorization: Bearer {myAPIKey}"`

**Example request:**

```bash
curl -L \
  -H 'Authorization: Bearer 89fa747a-e01b-5940-99c2-4e96fa996258' \
  'https://api.mobile-text-alerts.com/v3/auth/verify-api-key'
```

See [Get an API Key](/getting-started/get-an-api-key.md) to learn how to generate and send this key in a request.

### Content-Type

Content-Type is an HTTP header that indicates the data type of the request's message body. This allows the server to understand how to process the request data.

{% hint style="info" %}
All `POST` and `PATCH` requests to the Mobile Text Alerts API must include `Content-Type: application/json`
{% endhint %}

**Header structure:** `"Content-Type: application/json"`

**Example request:**

```bash
curl --location 'https://api.mobile-text-alerts.com/v3/groups/12345/subscribers/bulk-create' \
--header 'Content-Type: application/json' \
--data '{
    "subscriberIds": [
        123
    ]
}'
```

## Response Headers

Response headers provide metadata about the response to the client. Most of the Mobile Text Alerts API response headers provide information about your account's [rate limit](/api-basics/rate-limits.md) usage.

<table><thead><tr><th width="180">Parameter</th><th width="120">Type</th><th>Description</th></tr></thead><tbody><tr><td><code>RateLimit-Limit</code></td><td><code>integer</code></td><td>The maximum number of requests that the consumer is permitted to make per window.</td></tr><tr><td><code>RateLimit-Remaining</code></td><td><code>integer</code></td><td>The number of requests remaining in the current rate limit window.</td></tr><tr><td><code>RateLimit-Reset</code></td><td><code>integer</code></td><td>The remaining window before the rate limit resets (in milliseconds).</td></tr><tr><td><code>Retry-After</code></td><td><code>integer</code></td><td>The number of seconds to wait before retrying the request.</td></tr><tr><td><code>X-RateLimit-Limit</code></td><td><code>integer</code></td><td>The maximum number of requests that the consumer is permitted to make per window.</td></tr><tr><td><code>X-RateLimit-Remaining</code></td><td><code>integer</code></td><td>The number of requests remaining in the current rate limit window.</td></tr><tr><td><code>X-RateLimit-Reset</code></td><td><code>integer</code></td><td>The remaining window before the rate limit resets (in milliseconds).</td></tr><tr><td><code>X-Request-ID</code></td><td><code>string</code></td><td>A unique identifier for the request.</td></tr></tbody></table>


---

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