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What is curl?

curl, or cURL, is a command line tool used to transfer data to and from a server. It can execute HTTP requests with different parameters and methods.

curl lets you talk to a server by specifying the location (in the form of a URL) and the data you want to send.

curl and REST API documentation

REST APIs can use almost any programming language to call an endpoint. Documenting each programming language would be too time-consuming, so curl can be used to demonstrate the call.

If you make a curl request for a website, curl will retrieve and display the website's code.

For example, the following command:

curl https://example.com

returns the following response:

<!doctype html>
    <html>

    <head>
        <title>Example Domain</title>

        <meta charset="utf-8" />
        <meta http-equiv="Content-type" content="text/html; charset=utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1" />
        <style type="text/css">
            body {
                background-color: #f0f0f2;
                margin: 0;
                padding: 0;
                font-family: -apple-system, system-ui, BlinkMacSystemFont, "Segoe UI", "Open Sans", "Helvetica Neue", Helvetica, Arial, sans-serif;

            }

            div {
                width: 600px;
                margin: 5em auto;
                padding: 2em;
                background-color: #fdfdff;
                border-radius: 0.5em;
                box-shadow: 2px 3px 7px 2px rgba(0, 0, 0, 0.02);
            }

            a:link,
            a:visited {
                color: #38488f;
                text-decoration: none;
            }

            @media (max-width: 700px) {
                div {
                    margin: 0 auto;
                    width: auto;
                }
            }
        </style>
    </head>

    <body>
        <div>
            <h1>Example Domain</h1>
            <p>This domain is for use in illustrative examples in documents. You may use this
                domain in literature without prior coordination or asking for permission.</p>
            <p><a href="https://www.iana.org/domains/example">More information...</a></p>
        </div>
    </body>

    </html>

If you were to request the same website on a browser, then the browser would display the code in a way that’s visually readable.

curl, however, shows you what you're actually retrieving (code).

curl and Windows

  • Always use double-quotes instead of single-quotes
  • Don’t use backslashes (\) to separate lines
  • Add -k to the curl command to bypass curl’s security certificate (if necessary)

How to confirm if you have curl installed

Run the following command from the command line:

curl --version

The response should look like this:

curl 7.83.1 (Windows) libcurl/7.83.1 Schannel
Release-Date: 2022-05-13
Protocols: dict file ftp ftps http https imap imaps pop3 pop3s smtp smtps telnet tftp
Features: AsynchDNS HSTS IPv6 Kerberos Largefile NTLM SPNEGO SSL SSPI UnixSockets
Sources