Cloudflare Turnstile solver in C# and .NET

Solve Cloudflare Turnstile in C# and .NET: a tested example that gets a Cloudflare Turnstile token from the ZeroCaptcha API with HttpClient and System.Text.Json, with retries, idempotency keys and cancellation. .NET 8+.

Website · Docs · Quickstart · API reference · Pricing

What it does

TurnstileSolver gets a valid Cloudflare Turnstile token for a page you are allowed to automate, and the TurnstileSolver console app prints one. You give it the page's URL and the widget's sitekey; it creates a task on the ZeroCaptcha API, waits for it, and returns the token to submit as the browser would.

• No packages: HttpClient and System.Text.Json, as .NET 8 and later have them.
• Async and cancellable: SolveAsync takes a CancellationToken; give it a deadline, such as three minutes.
• Safe to retry: every task is created with its own Idempotency-Key, so a retry after a lost reply returns the same task instead of paying for a second one. 429, 502, 503 and 504 are retried after the wait the API asks for.
• Clear failures: a refusal or a failed task throws ZeroCaptchaException with the API's Code, such as insufficient_funds or ERROR_CAPTCHA_UNSOLVABLE, and the RequestId to quote to support.

Quickstart

1. Create an account on the ZeroCaptcha website, create an API key on the dashboard and add funds (crypto, from $10). A task is charged only when it succeeds.

2. Put the API's address and your key in your environment, never in your code:

   export ZEROCAPTCHA_API=https://api.zerocaptcha.io
   export ZEROCAPTCHA_KEY=zc_live_...

3. Read the widget's data-sitekey, and its data-action and data-cdata if it sets them (the sitekey guide shows where else they hide, such as the options of turnstile.render()), then run:

   dotnet run --project src/TurnstileSolver -- https://shop.example.com/login 0x4AAAAAAAB1cD2eF3gH4iJ5 login session-7f3a9c2e

   Many sites check the action and cData when they verify the token, so pass both whenever the widget sets them.

   It prints the token. Set PROXY_URL=http://user:pass@proxy.example.net:8080 to solve through your own proxy.

Use it in your code

Copy src/TurnstileSolver/TurnstileSolver.cs into your project, and share one HttpClient (or use IHttpClientFactory):

var solver = new TurnstileSolver(httpClient, Environment.GetEnvironmentVariable("ZEROCAPTCHA_API")!, Environment.GetEnvironmentVariable("ZEROCAPTCHA_KEY")!);
using var deadline = new CancellationTokenSource(TimeSpan.FromMinutes(3));
try
{
    var token = await solver.SolveAsync(
        new TurnstileTask(
            "https://shop.example.com/login", // the page with the widget
            "0x4AAAAAAAB1cD2eF3gH4iJ5", // its data-sitekey
            // The widget's data-action and data-cdata, or turnstile.render()'s action and cData
            // options; leave out any the widget does not set.
            Action: "login",
            CData: "session-7f3a9c2e"),
        deadline.Token);
}
catch (ZeroCaptchaException error)
{
    logger.LogWarning("{Code} (request {RequestId})", error.Code, error.RequestId);
}

Submit the token

The widget sends its token in the cf-turnstile-response form field, and the site checks it with Cloudflare's siteverify when the form arrives. Send yours the same way, straight after you get it:

var form = new FormUrlEncodedContent(new Dictionary<string, string>
{
    ["email"] = "me@example.com",
    ["cf-turnstile-response"] = token,
});
var response = await httpClient.PostAsync("https://shop.example.com/login", form);

With Selenium or Playwright for .NET, set the field in the page instead: the Selenium and Playwright examples show the script, which is the same in every language.

How it works

1. POST /v1/tasks with the page, the sitekey, and the action and cData if the widget sets them. The task's price is held on your balance.
2. GET /v1/tasks/{id} every 2 seconds while the task is queued or running.
3. succeeded carries solution.token, and the held price is charged. failed or expired carries an errorCode, and the hold is released: nothing is charged.

The task lifecycle and the errors and retries guide have every detail.

Honest limits

• A token works once, for 300 seconds. Get it just before you submit, and a new one for the next submission.
• The action and cData must match the widget's. A token made without them can be refused by the site's siteverify check.
• Proxies are http or https, with the port in the URL. SOCKS is not supported.
• Only for sites you own or are allowed to automate. The Acceptable Use Policy applies to every task.

FAQ

Is there a NuGet package? Not yet: the official clients are for JavaScript, Python and Go. This one file is small enough to copy.

Does it work on .NET Framework? Not as written: it uses .NET 8's primary constructors and System.Text.Json nodes. The API calls are plain HTTP, so a port is short.

What does a solve cost? The pricing page lists the price per 1,000 solved tasks. Only a task that succeeds is charged.

Why is my token refused by the site? Most often it was used twice, used after 300 seconds, or made without the widget's action or cData. The siteverify errors article explains each code.

Run the tests

dotnet test tests/TurnstileSolver.Tests

The tests give the solver an HttpClient whose handler is a stand-in API: no network, no key, no real task, nothing spent.

More from ZeroCaptcha

• The website: ZeroCaptcha, the docs, the guides, the blog and the status page
• Start here: zerocaptcha, cloudflare-turnstile-solver, cloudflare-challenge-solver
• Examples by language: cloudflare-turnstile-solver-python, cloudflare-turnstile-solver-nodejs, cloudflare-turnstile-solver-go, cloudflare-turnstile-solver-php, cloudflare-turnstile-solver-java, cloudflare-turnstile-solver-csharp, cloudflare-turnstile-solver-rust
• Browser automation: cloudflare-turnstile-solver-playwright, cloudflare-turnstile-solver-puppeteer, cloudflare-turnstile-solver-selenium
• SDKs, MCP server and migration: zerocaptcha-js, zerocaptcha-python, zerocaptcha-go, zerocaptcha-mcp, createtask-api-migration
• Lists: awesome-cloudflare-turnstile

Licence

MIT: see LICENSE.

Disclaimer

ZeroCaptcha is an independent service, not affiliated with or endorsed by Cloudflare. Cloudflare and Turnstile are trademarks of Cloudflare, Inc. Use ZeroCaptcha only on sites you own or are allowed to automate, as the Acceptable Use Policy says; any site owner can opt out.