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

# Request Headers

> Learn how to configure HTTP headers for authentication, content types, and custom metadata in your API requests.

HTTP headers are key-value pairs that provide additional information about your request. They're essential for authentication, specifying content types, and sending custom metadata to the API.

## Understanding Headers

Headers serve multiple purposes in HTTP requests:

<CardGroup cols={2}>
  <Card title="Authentication" icon="key">
    Pass tokens, API keys, or credentials to authenticate with the API
  </Card>

  <Card title="Content Type" icon="file-code">
    Tell the server what format your data is in (JSON, XML, etc.)
  </Card>

  <Card title="Accept Type" icon="check">
    Specify what response format you expect from the server
  </Card>

  <Card title="Custom Metadata" icon="tag">
    Send additional information like user agent, tracking IDs, or custom flags
  </Card>
</CardGroup>

***

## Adding Headers

The **Headers** tab allows you to add Request Headers in your API request.
Each header consists of:

* **Key**: The header name (e.g., `Authorization`, `Content-Type`)
* **Value**: The header value
* **Description** (optional): Internal documentation to explain the purpose of this header

<img src="https://mintcdn.com/requestly/hxDG-lNXUZAdWoty/images/Headers-Create-Requests.png?fit=max&auto=format&n=hxDG-lNXUZAdWoty&q=85&s=6110acb3c0cefae6cc1cf3fac2130b31" alt="Headers - Send API Request" align="center" fullwidth="false" width="1446" height="1064" data-path="images/Headers-Create-Requests.png" />

<Tip>
  The checkboxes next to each header let you include or exclude them without deleting them. This is useful for testing with and without certain headers.
</Tip>

### Bulk Edit Headers

You can also manage headers using **Bulk Edit**. This allows you to add or update multiple headers at once in a `key:value` format.

**How to use:**

1. Click the **Bulk Edit** button in the Headers tab
2. Add one header per line
3. Separate keys and values using a colon `:`
4. Prefix any line with `//` to disable that header

**Example:**

```
Content-Type:application/json
Authorization:Bearer {{token}}
X-API-Version:v2
// X-Debug:true
```

<Tip>
  Bulk Edit is especially useful when copying headers from documentation or sharing with team members.
</Tip>

## Using Variables in Headers

You can use variables in header values to make them dynamic:

```
Key: Authorization
Value: Bearer {{authToken}}
```

<Info>
  Learn more about using variables in [Variables and Environments](/api-client/environments-and-variables).
</Info>

## Header Inheritance

Headers can be inherited from collections, making it easy to apply common headers across multiple requests:

**Collection-Level Headers** → **Request-Level Headers** → **Authorization Tab**

* **Collection-Level Headers**: Set headers at the collection level to apply them to all requests in that collection.
* **Request-Level Headers**: Override collection-level headers with the same key. Request-level headers have the highest priority.
* **Authorization Tab**: Headers set in the Authorization tab are applied in addition to manual headers and do not override them.

<Info>
  Headers are resolved from most-specific to least-specific. Request-level headers always win over collection-level headers when both define the same key.
</Info>

## What's Next?

<CardGroup cols={3}>
  <Card title="Add Authorization" icon="shield" href="/api-client/authorization">
    Use the Authorization tab for easier authentication setup
  </Card>

  <Card title="Use Scripts" icon="code" href="/api-client/send-api-request/save-and-manage-data">
    Dynamically generate headers with pre-request scripts
  </Card>

  <Card title="Environment Variables" icon="globe" href="/api-client/environments-and-variables">
    Learn how to use variables in headers
  </Card>
</CardGroup>