How to send a header using a HTTP request through a cURL call?

When using cURL for HTTP requests, you can add custom HTTP headers using the -H or --header option. This feature is particularly useful when calling APIs or including additional information in HTTP requests, such as authentication details or content types.

Basic Syntax

The basic cURL command syntax for adding HTTP headers is as follows:

bash
curl -H "Header-Key: Header-Value" [other options] URL

Here, Header-Key is the key for the HTTP header, and Header-Value is the corresponding value.

Examples

1. Sending a Request with a User-Agent

   To specify a custom user agent with cURL, use:

   bash
   

curl -H "User-Agent: MyCustomUserAgent/1.0" http://example.com

shell

2. **Sending Authentication Information**

   For APIs requiring basic authentication, send the encoded username and password via HTTP headers:

   ```bash
curl -H "Authorization: Basic YWRtaW46cGFzc3dvcmQ=" http://example.com

Here, YWRtaW46cGFzc3dvcmQ= represents the Base64-encoded username and password.

1. Specifying Content Type

   When sending JSON data using POST or PUT methods, set the content type to application/json:

   bash
   

curl -X POST -H "Content-Type: application/json" -d '{"name": "John", "age": 30}' http://example.com/users

shell

   This informs the server that the data is in JSON format.

4. **Adding Multiple Headers**

   To include multiple headers, specify each with a separate `-H` option:

   ```bash
curl -H "Authorization: Bearer YourAccessToken" -H "Content-Type: application/json" http://example.com/api/data

Notes

• Ensure headers are correctly formatted and comply with HTTP protocol specifications.
• Special characters may require proper escaping or quoting in the shell.
• Using the -v option displays header information in requests and responses, which is invaluable for debugging.

By leveraging the -H option in cURL, you can flexibly include any required HTTP headers in your HTTP requests.