# Headers in HTTL

Headers follow a simple `key: value` syntax.

## Syntax Rules:

```
Content-Type: application/json
```

- **Single-line requirement**: Headers must be declared on a single line.
- **Automatic trimming**: Leading/trailing whitespace in the value is automatically removed.

## Header Types:

1. **Request Headers**  
   - Apply to a specific HTTP request.  
   - Defined within a request block.
2. **Global Headers**  
   - Apply to all requests in the file.  
   - Declared outside of any request block.

* * *

### Request header

_(Partially covered in the Request section)_

Request headers are declared immediately after a request declaration and apply only to that specific request.

Example:

```
get /users
Authorization: Bearer token
Content-Type: application/json
Cache-Control: no-cache
```

* * *

### Global header

Global headers are automatically applied to all subsequent requests within the file.

These are particularly useful for defining:

- Authentication headers (e.g., `Authorization: Bearer <token>`)
- Common content types (e.g., `Content-Type: application/json`)
- API-wide configurations (e.g., `X-API-Version: 2.1`)

Example:

```
@base: https://reqres.in/api

Content-Type: application/json
Authorization: Bearer token

get /users

post /users {
  name: "morpheus",
  job: "leader"
}
```

* * *

**Note**

Headers are sent in lowercase in accordance with the [HTTP specification](https://datatracker.ietf.org/doc/html/rfc7540#section-8.1.2).

Last updated on April 2, 2025