Toolpaper

401 Unauthorized in JavaScript

The server accepted the request shape but rejected your credentials or scheme. Paste your curl command to see what JavaScript (fetch) would send and compare against the working request.

Quick answer

To convert a cURL command to JavaScript, paste it into the Toolpaper workbench below. It parses the command in your browser and emits idiomatic JavaScript code — headers, query string, request body, authentication (Bearer, Basic, API key), and cookies are all wired up automatically. No data is uploaded; conversion is fully client-side.

Prefer a different target? See the full cURL to JavaScript reference, or jump to the same guide in Node.js, Python, or Go.

InputcURL command
1 secret
MethodGET·Headers1·Body—· Chars 73
OutputJavaScript · fetch(browser/Node)
const response = await fetch("https://api.example.com/me", {
  method: "GET",
  headers: {
    "Authorization": "Bearer YOUR_TOKEN"
  },
  redirect: "manual"
});
const data = await response.json();
Inspect

Example

A representative curl command for this scenario. Paste your own above to convert an exact match.

curl input
curl https://api.example.com/me \
  -H "Authorization: Bearer YOUR_TOKEN"

Implementation notes

  • Double-check the Authorization header, ensure the token hasn't expired, and confirm the scheme (Bearer vs Basic vs API key) matches what the docs specify.
  • Use the Explain panel to enumerate exactly which headers, cookies, and TLS flags the curl request carries.
  • The In-browser Runner is a fast way to confirm whether the failure reproduces from the browser or only from the server.

Common mistakes

  • Comparing curl and JavaScript without capturing both actual wire requests — mitmproxy or Charles pays off here.
  • Assuming a working curl means the API is happy — client differences (redirect handling, keep-alive, HTTP/2) surface as edge cases.
  • Silencing warnings instead of fixing them — every JavaScript client has a way to log the outgoing request; turn it on.

Common questions

Why does curl work but JavaScript fail?
Usually a header curl adds by default is missing in JavaScript, or vice versa. Paste the curl above to see a normalized breakdown.
Is my request sent to Toolpaper?
No. Parsing and diffing run in your browser.

More guides in JavaScript

JavaScript hub →

CORS error when replaying curl in the browser · JavaScript

/how-to/curl-cors-in-javascript

SSL certificate error · JavaScript

/how-to/curl-ssl-in-javascript

The same guide in other languages

All guides →

In Node.js

/how-to/curl-401-in-node

In Python

/how-to/curl-401-in-python

In Go

/how-to/curl-401-in-go

In Java

/how-to/curl-401-in-java

In C#

/how-to/curl-401-in-csharp

Full JavaScript reference on the cURL to JavaScript hub, or open the main converter for all 18 targets.