Learn how to fix the “Cloudflare Response Code Mismatch” error. Our Cloudflare Support team is here to help you with your questions and concerns.

Cloudflare Response Code Mismatch Error | Fixed

According to our Experts, the “Cloudflare Response Code Mismatch Error” occurs when the HTTP status code returned by Cloudflare, acting as a proxy, differs from the status code sent by the origin server. This situation can result in failed page loads, API response errors, or other unexpected behavior for users trying to access a website or service.

In other words, the issue is usually caused by conflicts between Cloudflare’s caching, security settings, or configurations and the origin server’s response behavior.

An Overview:

• What Causes the Cloudflare Response Code Mismatch?
• 1. Cache Mismatch
• 2. Firewall Rules or Security Settings
• 3. Origin Server Configuration Issues
• 4. SSL/TLS Mismatches
• 5. Cloudflare-Generated Error Pages
• 6. API Gateway or WebSocket Configuration Issues
• How to Troubleshoot Cloudflare Response Code Mismatch
• Best Practices to Prevent Response Code Mismatches

What Causes the Cloudflare Response Code Mismatch?

When a user requests a resource, Cloudflare acts as an intermediary between the user’s browser and the origin server. This intermediary role serves to:

• Cache content for improved performance and reduced server load.
• Provide security features like DDoS protection, rate limiting, and firewall rules.

However, during this interaction, Cloudflare may alter or interpret the origin server’s response, leading to a mismatch in HTTP response codes. Let’s look at some of the common causes of this issue.

1. Cache Mismatch

Cloudflare may serve a cached response with a status code different from the one currently sent by the origin server. For example:

The origin server sends a `200 OK` response, but Cloudflare serves an older cached `404 Not Found` or `301 Moved Permanently` response.

Fix:

• Purge the cached resource in Cloudflare.
• Adjust cache settings to reduce Time-to-Live (TTL) values and ensure more frequent updates.

2. Firewall Rules or Security Settings

Cloudflare’s Web Application Firewall, rate limiting, or bot protection may block or challenge requests, resulting in mismatched response codes. For example, Cloudflare might return a `403 Forbidden` or `500 Internal Server Error` instead of the origin server’s `200 OK`.

Fix:

• Review and adjust firewall rules in the Cloudflare dashboard.
• Check settings like Bot Fight Mode, Browser Integrity Check, and IP Access Rules.
• Ensure rate limiting does not affect critical API endpoints or high-traffic areas.

3. Origin Server Configuration Issues

In some cases, the origin server may send specific HTTP status codes, but Cloudflare may interpret them differently. For example:

• The origin server sends a `301` redirect, but Cloudflare changes it to a `302` or `307`.
• Custom `500` error pages are overridden by Cloudflare’s generic error responses.

Fix:

• Review the origin server’s configuration for error handling and redirect logic.
• Ensure consistent handling of HTTP response codes at the origin server.

4. SSL/TLS Mismatches

Cloudflare’s SSL/TLS encryption settings may not align with the origin server, causing errors such as:

• Cloudflare returns a `525 SSL Handshake Failed` error when the origin server expects an unencrypted connection.

Fix:

• Use the Full (Strict) SSL mode to ensure secure communication between Cloudflare and the origin server.
• Install a valid SSL certificate on the origin server.

5. Cloudflare-Generated Error Pages

Cloudflare may generate its own error pages, which can differ from custom error pages configured on the origin server.

Fix:

• Customize Cloudflare’s error pages to match the origin server’s responses.
• Disable Cloudflare error handling for specific scenarios, if supported by our plan.

6. API Gateway or WebSocket Configuration Issues

When using APIs or WebSocket connections, mismatches may arise if Cloudflare interprets request/response behaviors differently. For example:

• Cloudflare returns a `101 Switching Protocols` response for WebSocket connections while the origin server expects a different HTTP code.

Fix:

Ensure API Gateway and WebSocket settings are correctly configured in both Cloudflare and the origin server.

How to Troubleshoot Cloudflare Response Code Mismatch

• First, identify if an incorrect response is cached. Use the Cloudflare dashboard or API to purge the cache for the affected resource:

  
curl -X POST "https://api.cloudflare.com/client/v4/zones/{zone_id}/purge_cache" \
-H "X-Auth-Email: {email}" \
-H "X-Auth-Key: {api_key}" \
-H "Content-Type: application/json" \
--data '{"purge_everything":true}'

• Then, use browser Developer Tools to compare response codes from Cloudflare and the origin server. This can help pinpoint where the mismatch occurs.
• If the error still occurs, review the error logs. We can check HTTP response codes and security events in the Cloudflare dashboard. Furthermore, compare response codes with Cloudflare logs to identify discrepancies.
• Also, temporarily pause Cloudflare or enable Development Mode to test the origin server directly. This helps determine whether the issue lies with Cloudflare or the server configuration.

Best Practices to Prevent Response Code Mismatches

• Always use secure communication settings. The Full (Strict) mode is recommended for maximum compatibility and security.
• Set appropriate cache TTL values and purge the cache when making significant updates to the origin server.
• Track logs from both Cloudflare and the origin server to identify and resolve discrepancies early.
• Ensure that custom error pages are properly configured on both the origin server and Cloudflare.
• Verify that redirects, error handling, and API/WebSocket configurations are consistent between Cloudflare and the origin server.

[Need assistance with a different issue? Our team is available 24/7.]

Conclusion

By following these troubleshooting steps and best practices, we can easily resolve the “Cloudflare Response Code Mismatch Error” and maintain a seamless user experience for our website or service.

In brief, our Support Experts demonstrated how to fix the “Cloudflare Response Code Mismatch” error.