Explainer1 min readUpdated July 7, 2026

What is cURL?

Short answer

cURL is a command-line tool that sends HTTP requests and prints the response. It is the standard way to test APIs and share a request, because a single curl line fully describes the method, headers, and body.

A request in one line

A curl command captures everything about a request: the URL, the method, the headers, and the body. That makes it the common language for sharing API calls in docs, bug reports, and between tools.

curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d '{"name":"Ada"}'

A POST request with curl

Flags you will see most

-X sets the HTTP method, such as GET, POST, QUERY, or DELETE
-H adds a request header
-d sends a request body, which implies POST unless -X says otherwise
-i includes the response headers in the output
-L follows redirects

Try it: cURL GeneratorBuild a curl command from a method, URL, headers, and body locally.Open tool

Watch out for secretsA curl command can contain API keys or tokens in its headers. Strip those before pasting a command into a public issue or chat.

References

Questions

Does -d always send a POST request?

By default, adding -d makes curl send a POST. You can override the method with -X, for example -X PUT or -X QUERY, while still sending the body with -d.

How do I see the response headers?

Add -i to include the response headers in the output, or -I to send a HEAD request and see only the headers.

Does this send my data anywhere?

No. Utilumo's developer tools parse and transform input inside the browser tab. Nothing is uploaded, stored, or logged.