How to send HTTP data with cURL

HTTP requests often carry data through query strings, request bodies, or headers to convey parameters, submit forms, or send JSON payloads. Handling these inputs correctly ensures meaningful server responses.

With cURL, various options enable submitting data in different formats, from URL-encoded fields to JSON or multipart/form-data. Aligning Content-Type headers and choosing the right submission method ensures proper server-side interpretation.

Mastering data transmission via cURL facilitates seamless API interactions, automated form submissions, and robust scripting workflows, maintaining consistency and reliability in data exchanges.

1. Open a terminal.
2. Include parameters in a GET request URL.

   $ curl "https://www.example.com/api?param1=value1&param2=value2"

3. Use --data to send form-encoded data in a POST request.

   $ curl --data "param1=value1&param2=value2" "https://www.example.com/api"

   By default, --data triggers POST with application/x-www-form-urlencoded.

4. Specify Content-Type: application/json for JSON payloads.

   $ curl --request POST --header "Content-Type: application/json" --data '{"key1":"value1","key2":"value2"}' "https://www.example.com/api"

   Ensure the Content-Type matches the API's expected format.

5. Use --request PUT to send data with the PUT method.

   $ curl --request PUT --data "param1=value1" "https://www.example.com/api"

   The method changes with --request, while --data provides the payload.

6. Use --form for multipart/form-data (e.g., file uploads).

   $ curl --form "file=@path_to_file" "https://www.example.com/upload"

   Multipart uploads are essential for file submissions.

7. Add headers with --header for authentication or metadata.

   $ curl --header "Authorization: Bearer YOUR_TOKEN" --data "param=value" "https://www.example.com/api"

   Include tokens or custom directives in headers.

8. Use --insecure in development to bypass SSL checks if needed.

   $ curl --insecure --data "param=value" "https://www.example.com/api"

   --insecure is unsafe for production, use only in trusted tests.