What Is cURL? Command Line Tool Explained

This article provides a concise overview of cURL, detailing what the tool is, how it works across various network protocols, and why developers rely on it for testing APIs and transferring data. You will also learn about its core component, libcurl, and find resources to explore its complete command-line capabilities.

cURL, which stands for "Client URL," is an open-source command-line tool and library used for transferring data to and from a server using various network protocols. Created by Daniel Stenberg in 1997, it has become a fundamental utility in software development, system administration, and automation. At its core, cURL is powered by libcurl, a portable and robust transfer library that allows developers to integrate network transfer capabilities directly into their own applications.

The tool supports a vast range of internet protocols, including HTTP, HTTPS, FTP, FTPS, SFTP, SCP, IMAP, POP3, and SMTP. Because of this broad compatibility, cURL operates seamlessly across virtually all operating systems, including Linux, macOS, and modern versions of Windows.

In practical use, cURL is most frequently employed to interact with RESTful APIs and web services. Developers use it directly within the terminal to send HTTP requests—such as GET, POST, PUT, and DELETE—without needing a graphical user interface or a browser. It enables users to inspect HTTP headers, follow redirects, pass authentication credentials, submit form data, and upload or download files.

Because cURL outputs raw response data directly to the command line, it easily integrates into shell scripts and CI/CD deployment pipelines. This makes it an ideal tool for automating tasks like health checks, endpoint monitoring, and automated data backups.

For comprehensive syntax guides, flags, and advanced command examples, refer to this online documentation website for cURL to explore everything the tool can do.