cURL Builder

How to use cURL Builder

1. Open cURL Builder — it runs entirely in your browser with no setup.
2. Paste or type your input into the text area, or upload a file where supported.
3. Set any options you need. The result appears in the output panel — there is no upload step and no waiting on a server.
4. Review the output instantly; large inputs are handled locally without lag.
5. Copy the result to your clipboard or download it. Your data never leaves the page.

Why use cURL Builder?

• 100% free with no limits, no sign-up and no watermarks.
• Private by design — your data are processed in your browser and never uploaded to a server.
• Fast and lightweight, with instant results even on a phone or a slow connection.
• Works everywhere — any modern browser on Windows, macOS, Linux, Android or iOS.
• Part of a full developer tools suite, so related curl builder tasks are one click away.

What people use cURL Builder for

• Constructing a curl command for an API call without memorising the flags.
• Producing a reproducible request to paste into a bug report or runbook.
• Testing an endpoint with custom headers and a JSON body.

cURL Builder: limits and things worth knowing

• A secret placed in a command line is exposed: it lands in your shell history and is visible in the process list to other users on the machine. Use --data @file or an environment variable for anything sensitive.
• -d implies POST and sets a form content type, so a JSON body needs -H 'Content-Type: application/json' explicitly or the server will misparse it.
• Single-quote the URL whenever it contains & or ?, or the shell will interpret them before curl ever sees them.
• The command is assembled in your browser; nothing you type — including tokens — is transmitted anywhere.

Is it private and secure?

Your privacy is built in. cURL Builder runs completely on your device, so whatever you enter stays in your browser and is never transmitted, logged or stored on any server.

Network activity: none. Nothing is sent and nothing is fetched. This tool makes no network request at all once the page has loaded — which is why it keeps working if your connection drops.

You do not have to take that on trust — our privacy proof page publishes the Content-Security-Policy that enforces it, lists every third party it permits, and shows how to verify the whole claim yourself.

Learn more

Is It Safe to Paste Production Data Into Online Tools? — JWTs, API responses and env files get pasted into online formatters every day. Here's what actually happens to that data and how to check before you paste.