--- title: Validate the token description: Validate Turnstile tokens on your server with the siteverify API. image: https://developers.cloudflare.com/core-services-preview.png --- > Documentation Index > Fetch the complete documentation index at: https://developers.cloudflare.com/turnstile/llms.txt > Use this file to discover all available pages before exploring further. [Skip to content](#%5Ftop) # Validate the token Learn how to securely validate Turnstile tokens on your server using the Siteverify API. Mandatory server-side validation You must call the Siteverify API to complete your Turnstile implementation. The client-side widget alone does not protect your forms. Server-side validation is required because: * **Tokens can be forged.** An attacker can submit any string to your form endpoint without completing a challenge. * **Tokens expire.** Each token is valid for 300 seconds (5 minutes) after generation. * **Tokens are single-use.** Each token can only be validated once. A replayed token will be rejected with the `timeout-or-duplicate` error code. ## Process 1. Client generates token: Visitor completes Turnstile challenge on your webpage. 2. Token sent to server: Form submission includes the Turnstile token. 3. Server validates token: Your server calls Cloudflare's Siteverify API. 4. Cloudflare responds: Returns `success` or `failure` and additional data. 5. Server takes action: Allow or reject the original request based on validation. ## Siteverify API overview Endpoint ``` POST https://challenges.cloudflare.com/turnstile/v0/siteverify ``` ### Request format The API accepts both `application/x-www-form-urlencoded` and `application/json` requests, but always returns JSON responses. #### Required parameters | Parameter | Required | Description | | ---------------- | -------- | ------------------------------------------------------- | | secret | Yes | Your widget's secret key from the Cloudflare dashboard | | response | Yes | The token from the client-side widget | | remoteip | No | The visitor's IP address | | idempotency\_key | No | A UUID you generate to safely retry validation requests | #### Token characteristics * Maximum length: 2048 characters * Validity period: 300 seconds (5 minutes) from generation * Single use: Each token can only be validated once * Automatic expiry: Tokens automatically expire and cannot be reused The validation token issued by Turnstile is valid for five minutes. If a user submits the form after this period, the token is considered expired. In this scenario, the server-side verification API will return a failure, and the `error-codes` field in the response will include `timeout-or-duplicate`. To ensure a successful validation, the visitor must initiate the request and submit the token to your backend within the five-minute window. Otherwise, the Turnstile widget needs to be refreshed to generate a new token. This can be done using the `turnstile.reset` function. --- ## Basic validation examples * [ JavaScript ](#tab-panel-11366) * [ PHP ](#tab-panel-11367) * [ Python ](#tab-panel-11368) * [ Java ](#tab-panel-11369) * [ C# ](#tab-panel-11370) #### JSON JavaScript ``` const SECRET_KEY = "your-secret-key"; async function validateTurnstile(token, remoteip) { try { const response = await fetch( "https://challenges.cloudflare.com/turnstile/v0/siteverify", { method: "POST", headers: { "Content-Type": "application/json", }, body: JSON.stringify({ secret: SECRET_KEY, response: token, remoteip: remoteip, }), }, ); const result = await response.json(); return result; } catch (error) { console.error("Turnstile validation error:", error); return { success: false, "error-codes": ["internal-error"] }; }} ``` #### Form Data JavaScript ``` const SECRET_KEY = "your-secret-key"; async function validateTurnstile(token, remoteip) { const formData = new FormData(); formData.append("secret", SECRET_KEY); formData.append("response", token); formData.append("remoteip", remoteip); try { const response = await fetch( "https://challenges.cloudflare.com/turnstile/v0/siteverify", { method: "POST", body: formData, }, ); const result = await response.json(); return result; } catch (error) { console.error("Turnstile validation error:", error); return { success: false, "error-codes": ["internal-error"] }; }} // Usage in form handlerasync function handleFormSubmission(request) { const body = await request.formData(); const token = body.get("cf-turnstile-response"); const ip = request.headers.get("CF-Connecting-IP") || request.headers.get("X-Forwarded-For") || "unknown"; const validation = await validateTurnstile(token, ip); if (validation.success) { // Token is valid - process the form console.log("Valid submission from:", validation.hostname); return processForm(body); } else { // Token is invalid - reject the submission console.log("Invalid token:", validation["error-codes"]); return new Response("Invalid verification", { status: 400 }); }} ``` ``` $secret, 'response' => $token ]; if ($remoteip) { $data['remoteip'] = $remoteip; } $options = [ 'http' => [ 'header' => "Content-type: application/x-www-form-urlencoded\r\n", 'method' => 'POST', 'content' => http_build_query($data) ] ]; $context = stream_context_create($options); $response = file_get_contents($url, false, $context); if ($response === FALSE) { return ['success' => false, 'error-codes' => ['internal-error']]; } return json_decode($response, true); } // Usage$secret_key = 'your-secret-key';$token = $_POST['cf-turnstile-response'] ?? '';$remoteip = $\_SERVER['HTTP_CF_CONNECTING_IP'] ??$\_SERVER['HTTP_X_FORWARDED_FOR'] ??$\_SERVER['REMOTE_ADDR']; $validation = validateTurnstile($token, $secret_key, $remoteip); if ($validation['success']) {// Valid token - process formecho "Form submission successful!";// Process your form data here} else {// Invalid token - show errorecho "Verification failed. Please try again.";error_log('Turnstile validation failed: ' . implode(', ', $validation['error-codes']));}?> ``` Python ``` import requests def validate_turnstile(token, secret, remoteip=None): url = 'https://challenges.cloudflare.com/turnstile/v0/siteverify' data = { 'secret': secret, 'response': token } if remoteip: data['remoteip'] = remoteip try: response = requests.post(url, data=data, timeout=10) response.raise_for_status() return response.json() except requests.RequestException as e: print(f"Turnstile validation error: {e}") return {'success': False, 'error-codes': ['internal-error']} # Usage with Flaskfrom flask import Flask, request, jsonify app = Flask(__name__)SECRET_KEY = 'your-secret-key' @app.route('/submit-form', methods=['POST'])def submit_form(): token = request.form.get('cf-turnstile-response') remoteip = request.headers.get('CF-Connecting-IP') or \ request.headers.get('X-Forwarded-For') or \ request.remote_addr validation = validate_turnstile(token, SECRET_KEY, remoteip) if validation['success']: # Valid token - process form return jsonify({'status': 'success', 'message': 'Form submitted successfully'}) else: # Invalid token - reject submission return jsonify({ 'status': 'error', 'message': 'Verification failed', 'errors': validation['error-codes'] }), 400 ``` ``` import org.springframework.web.client.RestTemplate;import org.springframework.util.LinkedMultiValueMap;import org.springframework.util.MultiValueMap;import org.springframework.http.HttpEntity;import org.springframework.http.HttpHeaders;import org.springframework.http.MediaType;import org.springframework.http.ResponseEntity; @Servicepublic class TurnstileService {private static final String SITEVERIFY_URL = "https://challenges.cloudflare.com/turnstile/v0/siteverify";private final String secretKey = "your-secret-key";private final RestTemplate restTemplate = new RestTemplate(); public TurnstileResponse validateToken(String token, String remoteip) { HttpHeaders headers = new HttpHeaders(); headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED); MultiValueMap params = new LinkedMultiValueMap<>(); params.add("secret", secretKey); params.add("response", token); if (remoteip != null) { params.add("remoteip", remoteip); } HttpEntity> request = new HttpEntity<>(params, headers); try { ResponseEntity response = restTemplate.postForEntity( SITEVERIFY_URL, request, TurnstileResponse.class); return response.getBody(); } catch (Exception e) { TurnstileResponse errorResponse = new TurnstileResponse(); errorResponse.setSuccess(false); errorResponse.setErrorCodes(List.of("internal-error")); return errorResponse; } } } // Controller usage@PostMapping("/submit-form")public ResponseEntity submitForm(@RequestParam("cf-turnstile-response") String token,HttpServletRequest request) { String remoteip = request.getHeader("CF-Connecting-IP"); if (remoteip == null) { remoteip = request.getHeader("X-Forwarded-For"); } if (remoteip == null) { remoteip = request.getRemoteAddr(); } TurnstileResponse validation = turnstileService.validateToken(token, remoteip); if (validation.isSuccess()) { // Valid token - process form return ResponseEntity.ok("Form submitted successfully"); } else { // Invalid token - reject submission return ResponseEntity.badRequest() .body("Verification failed: " + validation.getErrorCodes()); } } ``` ``` using System.Text.Json; public class TurnstileService{ private readonly HttpClient _httpClient; private readonly string _secretKey = "your-secret-key"; private const string SiteverifyUrl = "https://challenges.cloudflare.com/turnstile/v0/siteverify"; public TurnstileService(HttpClient httpClient) { _httpClient = httpClient; } public async Task ValidateTokenAsync(string token, string remoteip = null) { var parameters = new Dictionary { { "secret", _secretKey }, { "response", token } }; if (!string.IsNullOrEmpty(remoteip)) { parameters.Add("remoteip", remoteip); } var postContent = new FormUrlEncodedContent(parameters); try { var response = await _httpClient.PostAsync(SiteverifyUrl, postContent); var stringContent = await response.Content.ReadAsStringAsync(); return JsonSerializer.Deserialize(stringContent); } catch (Exception ex) { return new TurnstileResponse { Success = false, ErrorCodes = new[] { "internal-error" } }; } }} // Controller usage[HttpPost("submit-form")]public async Task SubmitForm([FromForm] string cfTurnstileResponse){ var remoteip = HttpContext.Request.Headers["CF-Connecting-IP"].FirstOrDefault() ?? HttpContext.Request.Headers["X-Forwarded-For"].FirstOrDefault() ?? HttpContext.Connection.RemoteIpAddress?.ToString(); var validation = await _turnstileService.ValidateTokenAsync(cfTurnstileResponse, remoteip); if (validation.Success) { // Valid token - process form return Ok("Form submitted successfully"); } else { // Invalid token - reject submission return BadRequest($"Verification failed: {string.Join(", ", validation.ErrorCodes)}"); }} ``` --- ## Advanced validation techniques Idempotency keys for retry operation ``` const crypto = require("crypto"); async function validateWithRetry(token, remoteip, maxRetries = 3) { const idempotencyKey = crypto.randomUUID(); for (let attempt = 1; attempt <= maxRetries; attempt++) { try { const formData = new FormData(); formData.append("secret", SECRET_KEY); formData.append("response", token); formData.append("remoteip", remoteip); formData.append("idempotency_key", idempotencyKey); const response = await fetch( "https://challenges.cloudflare.com/turnstile/v0/siteverify", { method: "POST", body: formData, }, ); const result = await response.json(); if (response.ok) { return result; } // If this is the last attempt, return the error if (attempt === maxRetries) { return result; } // Wait before retrying (exponential backoff) await new Promise((resolve) => setTimeout(resolve, Math.pow(2, attempt) * 1000), ); } catch (error) { if (attempt === maxRetries) { return { success: false, "error-codes": ["internal-error"] }; } } }} ``` Enhanced validation with custom checks ``` async function validateTurnstileEnhanced( token, remoteip, expectedAction = null, expectedHostname = null,) { const validation = await validateTurnstile(token, remoteip); if (!validation.success) { return { valid: false, reason: "turnstile_failed", errors: validation["error-codes"], }; } // Check if action matches expected value (if specified) if (expectedAction && validation.action !== expectedAction) { return { valid: false, reason: "action_mismatch", expected: expectedAction, received: validation.action, }; } // Check if hostname matches expected value (if specified) if (expectedHostname && validation.hostname !== expectedHostname) { return { valid: false, reason: "hostname_mismatch", expected: expectedHostname, received: validation.hostname, }; } // Check token age (warn if older than 4 minutes) const challengeTime = new Date(validation.challenge_ts); const now = new Date(); const ageMinutes = (now - challengeTime) / (1000 * 60); if (ageMinutes > 4) { console.warn(`Token is ${ageMinutes.toFixed(1)} minutes old`); } return { valid: true, data: validation, tokenAge: ageMinutes, };} // Usageconst result = await validateTurnstileEnhanced( token, remoteip, "login", // expected action "example.com", // expected hostname); if (result.valid) { // Process the request console.log("Validation successful:", result.data);} else { // Handle validation failure console.log("Validation failed:", result.reason);} ``` --- ## API response format * [ Successful response ](#tab-panel-11371) * [ Failed response ](#tab-panel-11372) Example ``` { "success": true, "challenge_ts": "2022-02-28T15:14:30.096Z", "hostname": "example.com", "error-codes": [], "action": "login", "cdata": "sessionid-123456789", "metadata": { "ephemeral_id": "x:9f78e0ed210960d7693b167e" }} ``` Example ``` { "success": false, "error-codes": ["invalid-input-response"]} ``` ### Response fields | Field | Description | | ---------------------- | ------------------------------------------------ | | success | Boolean indicating if validation was successful | | challenge\_ts | ISO 8601 timestamp when the challenge was solved | | hostname | Hostname where the challenge was served | | error-codes | Array of error codes (if validation failed) | | action | Custom action identifier from client-side | | cdata | Custom data payload from client-side | | metadata.ephemeral\_id | Device fingerprint ID (Enterprise only) | ### Error codes reference | Error code | Description | Action required | | ---------------------- | --------------------------------------- | ------------------------------------------------- | | missing-input-secret | Secret parameter not provided | Ensure secret key is included | | invalid-input-secret | Secret key is invalid or expired | Check your secret key in the Cloudflare dashboard | | missing-input-response | Response parameter was not provided | Ensure token is included | | invalid-input-response | Token is invalid, malformed, or expired | User should retry the challenge | | bad-request | Request is malformed | Check request format and parameters | | timeout-or-duplicate | Token has already been validated | Each token can only be used once | | internal-error | Internal error occurred | Retry the request | --- ## Implementation Example implementation ``` class TurnstileValidator { constructor(secretKey, timeout = 10000) { this.secretKey = secretKey; this.timeout = timeout; } async validate(token, remoteip, options = {}) { // Input validation if (!token || typeof token !== "string") { return { success: false, error: "Invalid token format" }; } if (token.length > 2048) { return { success: false, error: "Token too long" }; } // Prepare request const controller = new AbortController(); const timeoutId = setTimeout(() => controller.abort(), this.timeout); try { const formData = new FormData(); formData.append("secret", this.secretKey); formData.append("response", token); if (remoteip) { formData.append("remoteip", remoteip); } if (options.idempotencyKey) { formData.append("idempotency_key", options.idempotencyKey); } const response = await fetch( "https://challenges.cloudflare.com/turnstile/v0/siteverify", { method: "POST", body: formData, signal: controller.signal, }, ); const result = await response.json(); // Additional validation if (result.success) { if ( options.expectedAction && result.action !== options.expectedAction ) { return { success: false, error: "Action mismatch", expected: options.expectedAction, received: result.action, }; } if ( options.expectedHostname && result.hostname !== options.expectedHostname ) { return { success: false, error: "Hostname mismatch", expected: options.expectedHostname, received: result.hostname, }; } } return result; } catch (error) { if (error.name === "AbortError") { return { success: false, error: "Validation timeout" }; } console.error("Turnstile validation error:", error); return { success: false, error: "Internal error" }; } finally { clearTimeout(timeoutId); } }} // Usageconst validator = new TurnstileValidator(process.env.TURNSTILE_SECRET_KEY); const result = await validator.validate(token, remoteip, { expectedAction: "login", expectedHostname: "example.com",}); if (result.success) { // Process the request} else { // Handle failure console.log("Validation failed:", result.error);} ``` --- ## Testing You can test the dummy token generated with testing sitekey via Siteverify API with the testing secret key. Your production secret keys will reject dummy tokens. Refer to [Testing](https://developers.cloudflare.com/turnstile/troubleshooting/testing/) for more information. --- ## Best practices ### Security * Store your secret keys securely. Use environment variables or secure key management. * Validate the token on every request. Never trust client-side validation alone. * Check additional fields. Validate the action and hostname when specified. * Monitor for abuse and log failed validations and unusual patterns. * Use HTTPS. Always validate over secure connections. * Only call the Siteverify API in your backend environment. If you expose the secret key in the front-end client code to call Siteverify, attackers can bypass the security check. Ensure that your client-side code sends the validation token to your backend, and that your backend is the sole caller of the Siteverify API. ### Performance * Set reasonable timeouts. Do not wait indefinitely for Siteverify responses. * Implement retry logic and handle temporary network issues. * Cache validation results for the same token, if it is needed for your flow. * Monitor your API latency. Track the Siteverify response time. ### Error handling * Have fallback behavior for API failures. * Use user-friendly messaging. Do not expose internal error details to users. * Properly log errors for debugging without exposing secrets. * Rate limit to protect against validation flooding. ```json {"@context":"https://schema.org","@type":"TechArticle","@id":"https://developers.cloudflare.com/turnstile/get-started/server-side-validation/#page","headline":"Validate the token ยท Cloudflare Turnstile docs","description":"Validate Turnstile tokens on your server with the siteverify API.","url":"https://developers.cloudflare.com/turnstile/get-started/server-side-validation/","inLanguage":"en","image":"https://developers.cloudflare.com/core-services-preview.png","dateModified":"2026-05-05","publisher":{"@type":"Organization","name":"Cloudflare","url":"https://www.cloudflare.com/"},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"},"keywords":["REST API"]} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/turnstile/","name":"Turnstile"}},{"@type":"ListItem","position":3,"item":{"@id":"/turnstile/get-started/","name":"Get started"}},{"@type":"ListItem","position":4,"item":{"@id":"/turnstile/get-started/server-side-validation/","name":"Validate the token"}}]} ```