What is cURL?
Turkish: cURL
cURL is a command-line tool for sending URL-based requests, inspecting responses, and automating API tests or diagnostics.
What is cURL?
cURL is an open-source command-line client for sending and receiving data over HTTP, HTTPS, FTP, SFTP, and related protocols. It lets developers call an endpoint without a browser or graphical tool, inspect headers, view status codes, and save response bodies for debugging.
For example, when a payment API returns an unexpected error, a developer can send the same request with curl -X POST. That makes it easier to separate application bugs from authentication, network, TLS, or upstream service issues.
How Does cURL Work?
cURL receives a URL, HTTP method, headers, request body, and optional authentication details, then sends the request through the libcurl library using the selected protocol. When the response arrives, it can print headers and body to the terminal, write output to a file, or expose timing data.
Common options include:
-X: Sets the HTTP method, such asPOSTorPUT-H: Adds headers likeAuthorizationorContent-Type-d: Sends a JSON, form, or plain-text body-I: Shows response headers only-L: Follows redirect chains
Where Is It Used?
cURL is useful for reproducible API documentation examples, CI health checks, webhook testing, and validating a single request before broader load testing. Postman gives teams a visual workspace, while cURL commands are easy to paste into terminals, shell scripts, and automation jobs.
In API testing, recording the cURL command together with status code, response time, TLS errors, and response body makes integration incidents easier to investigate later.