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CORS error in C#

curl doesn't enforce CORS. Fetch and Axios do. A working curl doesn't mean a working browser call. Paste your curl command to see what C# (HttpClient) would send and compare against the working request.

Quick answer

To convert a cURL command to C#, paste it into the Toolpaper workbench below. It parses the command in your browser and emits idiomatic C# 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 C# reference, or jump to the same guide in JavaScript, Node.js, or Python.

InputcURL command
1 secret
MethodGET·Headers1·Body—· Chars 73
Output.NET · HttpClient(.NET)
using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;

class Program {
  static async Task Main() {
    using var handler = new HttpClientHandler { AllowAutoRedirect = false };
    using var client = new HttpClient(handler);
    using var request = new HttpRequestMessage(new HttpMethod("GET"), "https://api.example.com/me");
    request.Headers.TryAddWithoutValidation("Authorization", "Bearer YOUR_TOKEN");
    using var response = await client.SendAsync(request);
    var text = await response.Content.ReadAsStringAsync();
    Console.WriteLine(text);
  }
}
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

  • Move the call server-side, or ask the API to add your origin to Access-Control-Allow-Origin. The In-browser Runner surfaces CORS blockers explicitly.
  • 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 C# 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 C# client has a way to log the outgoing request; turn it on.

Common questions

Why does curl work but C# fail?
Usually a header curl adds by default is missing in C#, 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 C#

C# hub →

401 Unauthorized from curl · C#

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

SSL certificate error · C#

/how-to/curl-ssl-in-csharp

The same guide in other languages

All guides →

In JavaScript

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

In Node.js

/how-to/curl-cors-in-node

In Python

/how-to/curl-cors-in-python

In Go

/how-to/curl-cors-in-go

In Java

/how-to/curl-cors-in-java

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