cURL to Node.js

What is curl-to-Node?

This tool converts a curl command into a Node.js script that uses the built-in fetch API — the same fetch signature browsers use, available globally in Node 18+ without installing axios, node-fetch, or any other package.

How it works

The curl command is tokenized and parsed into method, url, headers, body, form fields, and auth. Each maps onto fetch's second argument: method, a headers object, and a body string taken verbatim from -d/--data — never re-parsed as JSON and re-serialized, so the exact bytes curl would send are preserved. -u user:pass is the one flag that needs a small computation rather than a straight mapping: fetch has no native "basic auth" option, so the generator emits Buffer.from('user:pass').toString('base64') at the top of the script and injects it into an Authorization header built from a template literal (Basic plus the credentials) — computed at runtime rather than baked in as a precomputed string, since Buffer is a Node global available wherever the script actually executes.

Features

• Zero-install output — uses global fetch, no npm install required
• Body passed through as a raw string, not re-encoded
• -u Basic Auth computed via Buffer.from(...).toString('base64') at runtime
• -F/--form uploads become a FormData instance, with file fields stubbed for you to attach real bytes
• Uses top-level await, so it runs directly as an ES module without wrapping in an async function

Example

Input: curl -X POST https://api.example.com/v1/login -H "Content-Type: application/json" -u admin:s3cret -d '{"username":"admin","remember":true}'

Output:

const credentials = Buffer.from('admin:s3cret').toString('base64');

const response = await fetch('https://api.example.com/v1/login', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'Authorization': `Basic ${credentials}`,
  },
  body: '{"username":"admin","remember":true}',
});

const data = await response.text();
console.log(response.status, data);

Common errors

Top-level await only works in an ES module context — either a file with a .mjs extension, or a "type": "module" entry in package.json. In a plain CommonJS .js file you'll get a syntax error and need to wrap the code in an async function. Also, running the output on Node < 18 fails with "fetch is not defined" — either upgrade Node or install node-fetch and add the import.

Best practices

Check response.ok before trusting the body — unlike some other HTTP clients, fetch doesn't throw on 4xx/5xx status codes, only on network failures. Wrap the call in a try/catch for those network-level errors, and avoid logging the raw credentials variable anywhere in production logs.