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How to Fix Error 521 with WordPress and Cloudflare

Error 521 is a common issue that WordPress users may encounter when using Cloudflare as their content delivery network (CDN). This error occurs when Cloudflare cannot establish a TCP connection to the origin server, resulting in website downtime. 

To resolve error 521, it is essential to troubleshoot both the WordPress site and the Cloudflare settings. 

This guide will discuss how to fix error 521 with WordPress and Cloudflare, addressing common WP errors and fixing WordPress issues along the way. 

By following the steps outlined in this guide, you can quickly identify the root cause of the issue and implement the necessary fixes to get your website back online. 

Why should you care about Cloudflare error codes? 

Understanding and addressing Cloudflare error codes, such as Error 521, is crucial for several reasons: 

1. Website availability  

Cloudflare error codes serve as indicators of potential issues that can impact the availability of your website.  

Error 521 explicitly indicates a communication breakdown between Cloudflare and the origin server, resulting in downtime. 

Identifying and resolving these errors promptly is essential to ensure that your website remains accessible to visitors and minimize disruptions to your online presence. 

2. User experience  

Encountering error messages such as error 521 when trying to access your site can significantly impact visitors’ experience. 

These errors can frustrate users, reduce their trust in your website, and potentially drive them to seek information or services elsewhere. 

Proactively addressing Cloudflare error codes can provide your audience with a seamless and reliable browsing experience, fostering positive interactions and engagement. 

3. SEO impact  

Website downtime or persistent errors can have detrimental effects on your search engine optimization (SEO) efforts. Search engines prioritize websites that offer consistent performance and accessibility to users. Therefore, unresolved Cloudflare error codes may result in lowered search engine rankings, reduced organic traffic, and diminished visibility in search results. 

Promptly resolving these errors can help maintain a healthy website performance that supports your SEO strategies and attracts organic traffic. 

4. Business reputation  

The reliability and availability of your website reflect your brand’s reputation and credibility.  

When your website has frequent errors and downtime, it can harm your business’s image and make it seem unreliable to your audience. 

Taking care of Cloudflare error codes promptly shows that you are committed to having a stable and trustworthy online presence, which can boost customer confidence in your brand and services. 

5. Security concerns  

Sometimes, Cloudflare error codes might indicate security issues or mistakes that could put your website at risk. Ignoring these errors could make your site vulnerable to cyber threats, data breaches, or other security risks. 

By actively monitoring and fixing Cloudflare error codes, you can make your website more secure and better protected against potential attacks, keeping sensitive information safe. 

What causes error 521 with WordPress and Cloudflare? 

Several factors can cause the occurrence of Cloudflare Error 521, including: 

1. Origin server downtime: If the origin server hosting your website is down or unreachable, Cloudflare’s edge servers will be unable to establish a connection, resulting in Error 521. 

2. Firewall restrictions: Strict firewall rules or security settings on the origin server can sometimes block incoming connections from Cloudflare’s IP addresses, leading to Error 521. 

3. Server configuration issues: Misconfigurations on the origin server, such as incorrect server settings, IP address restrictions, or network configurations, may prevent Cloudflare from establishing a connection and trigger Error 521. 

4. Traffic overload: Sudden spikes in traffic or high server load can overwhelm the origin server, preventing it from responding to requests from Cloudflare and resulting in Error 521. 

5. DNS resolution problems: Issues with DNS resolution, such as incorrect DNS settings or delays in DNS propagation, can hinder Cloudflare from reaching the origin server, resulting in Error 521. 

6. SSL/TLS certificate mismatch: If the SSL/TLS certificate installed on the origin server does not match the settings configured in Cloudflare, the handshake will fail, triggering Error 521. 

7. Routing or network connectivity issues: Problems with routing or network connectivity between Cloudflare’s edge servers and the origin server can disrupt communication and cause Error 521. 

How to fix the Cloudflare error 521 in five steps? 

Step 1: Check whether your server is offline 

1. Server availability check: 

Access your server directly by entering the server’s IP address or domain in a web browser. A successful response indicates that the server is functioning correctly. If you can reach your server directly, the issue may lie in the communication between Cloudflare and the origin server. 

2. Check server logs: 

Review the server logs to identify any recent errors or issues impacting its availability. Look for error messages indicating server downtime or connectivity problems. Analyze the logs for indications of high server load, network issues, firewall blocks, or other factors that could prevent Cloudflare from reaching the server. 

3. Verify firewall settings: 

Ensure that your server’s firewall settings allow incoming connections from Cloudflare’s IP addresses. Check for any rules blocking Cloudflare’s requests and adjust the firewall configuration accordingly. Whitelist Cloudflare’s IP ranges to allow traffic from their network to reach your server without being blocked by security measures. 

4. Test server response: 

Run diagnostic tools or commands like ping or traceroute to test the response time and connectivity between Cloudflare’s edge servers and your origin server. Verify that the server responds to Cloudflare requests promptly and that there are no network issues causing delays or interruptions. 

5. Update DNS settings: 

Ensure that your DNS settings point to the correct IP address of your origin server. Make any necessary adjustments to the DNS records to ensure that Cloudflare can successfully resolve the server’s address. Check for any DNS propagation issues that may be delaying the resolution of your server’s IP address and update the settings as needed. 

Step 2: Whitelist all of Cloudflare’s IP addresses  

Whitelisting Cloudflare’s IP addresses on your server is important in resolving Cloudflare Error 521 and ensuring smooth communication between Cloudflare’s edge servers and your origin server. 

Here’s how to effectively whitelist Cloudflare’s IP addresses: 

1. Obtain Cloudflare’s IP ranges: 

Cloudflare provides a list of IP address ranges used by their edge servers. This list is in the Cloudflare dashboard under the Firewall or Network settings. Make sure to have the most up-to-date list of Cloudflare’s IP ranges to whitelist all the relevant addresses. 

2. Access server firewall settings: 

To access the firewall settings, log in to your server’s control panel or terminal. You may use tools like iptables (Linux), Windows Firewall (Windows Server), or a third-party firewall management interface. 

3. Whitelist Cloudflare IP addresses: 

Add rules to allow incoming connections from Cloudflare’s IP ranges. Depending on your server setup, you can create specific rules to permit HTTP (port 80) and HTTPS (port 443) traffic from Cloudflare’s IPs. Ensure that the rules are configured to accept incoming connections from Cloudflare’s IP addresses and that they do not conflict with existing firewall rules. 

4. Test connectivity: 

After whitelisting Cloudflare’s IP addresses: 

  • Test the connectivity between Cloudflare’s edge servers and your origin server. 
  • Use tools like cURL or online services to send requests from Cloudflare’s network to your server and verify that the connections are successful. 
  • Monitor the server logs for any blocked requests or errors that could indicate issues with the whitelisting configuration. 

5. Regularly update IP Whitelists: 

Cloudflare periodically updates its IP address ranges as it expands its network. It is essential to stay informed about these updates and adjust your whitelist accordingly to ensure continued communication with Cloudflare’s servers. Set up a process to regularly review and update the whitelisted IP addresses to maintain secure and reliable connectivity between Cloudflare and your server. 

Step 3: Ask your hosting provider to enable port 443  

When encountering Cloudflare error 521, reaching out to your hosting provider to enable port 443 can be a crucial step in resolving the issue and ensuring secure communication between Cloudflare’s edge servers and your origin server. Here’s an overview of how you can effectively address this point: 

1. Identify the issue: 

Before contacting your hosting provider, make sure that Error 521 is caused by port 443 being disabled on your server. Port 443 is crucial for HTTPS connections, and enabling it will help establish secure communication channels. 

2. Contact support: 

Contact your hosting provider’s support team through live chat, email, or phone support. Clearly explain the issue with Error 521 and request help enabling port 443 on your server. 

3. Provide server details: 

When contacting your hosting provider, share relevant server information such as the server type (e.g., Apache, Nginx), server configuration, and operating system. This information will help the support team accurately enable port 443 on your server. 

4. Request port activation: 

Emphasize enabling port 443 on your server to facilitate secure HTTPS connections. Stress that enabling port 443 is crucial for resolving Error 521 and ensuring secure data transmission between Cloudflare and your server. 

5. Verify activation: 

After your hosting provider activates port 443, confirm that the port is open for HTTPS traffic. Use network diagnostic tools or commands to check the status of port 443 and ensure that it is accessible for secure connections. 

6. Test connectivity: 

Once port 443 is enabled, test the connectivity between Cloudflare and your origin server by initiating HTTPS requests. Monitor network logs or use online tools to confirm that HTTPS traffic is successfully reaching your server, indicating that port 443 activation has resolved Error 521. 

 Step 4: Create and upload a Cloudflare origin certificate  

1. Generate a Cloudflare origin certificate: 

Log in to your Cloudflare account and go to the SSL/TLS section. 

Look for the Origin Certificates tab or a similar option to create a new certificate. 

Click the “Create Certificate” button to generate a Cloudflare Origin Certificate. Follow the prompts to specify the certificate validity period and any additional settings required. 

2. Download the certificate files: 

After creating the Cloudflare Origin Certificate, download the certificate files to your local system. These files typically include the certificate itself, the private key, and any intermediate certificates necessary for the chain of trust. 

3. Upload the certificate to your server: 

Access your server’s control panel or SSH terminal to upload the Cloudflare Origin Certificate files. Depending on your server configuration, you may need to place the certificate files in specific directories or upload them through the server interface. 

Also, ensure that you securely transfer the certificate files to your server and that the private key remains confidential and protected. 

4. Configure SSL/TLS settings: 

Once the certificate files are uploaded to your server, configure your SSL/TLS settings to associate the Cloudflare Origin Certificate with your domain. Update the server configuration files (e.g., Apache config, Nginx config) to use the certificate for HTTPS connections. 

5. Restart the server: 

After updating the SSL/TLS settings, restart your web server to apply the changes and activate the Cloudflare Origin Certificate. This step ensures the server recognizes the new certificate and establishes secure connections using HTTPS on port 443. 

6. Test connectivity and encryption: 

Verify that the Cloudflare Origin Certificate is correctly installed by testing the HTTPS connectivity between Cloudflare and your origin server. Use online tools or browsers to confirm that secure HTTPS connections are established without errors. 

Next, check the browser address bar for encryption details to ensure that the connection is secure and that the Cloudflare Origin Certificate is being utilized. 

Step 5: Contact your hosting provider 

1. Identify the issue: 

Before contacting your hosting provider, make sure that Error 521 is caused by server-related issues or misconfigurations. Understanding the root cause will help you explain the problem effectively to the support team. 

2. Choose the communication channel: 

Contact your hosting provider through their support channels, which may include live chat, email, ticketing systems, or phone support. Select the communication method that best suits your urgency and preference for resolving the issue. 

3. Describe the error: 

Clearly describe the Cloudflare Error 521 you are experiencing and provide specific details, such as when the error started occurring, the impact on your website’s availability, and any troubleshooting steps you have already taken. 

4. Request assistance: 

Ask your hosting provider to assist in investigating the connectivity issues between Cloudflare and your server. Request them to check server logs, firewall settings, and server configurations to identify any issues causing Error 521. 

5. Provide server details: 

Share relevant server information with the support team, including your server type (e.g., Apache, Nginx), hosting plan, and any specific configurations that may affect communication with Cloudflare’s edge servers. 

6. Collaborate on solutions: 

Work collaboratively with your hosting provider to troubleshoot and resolve the connectivity issues causing Error 521. Follow their instructions, provide any additional information they request, and implement suggested solutions to address the problem effectively. 

7. Follow up and verify fixes: 

After your hosting provider takes action to resolve the issue, follow up to ensure that the connectivity problems are resolved. Test the connection between Cloudflare and your server to verify that Error 521 has been successfully addressed. 

8. Seek additional guidance: 

If your hosting provider’s initial solutions do not resolve Error 521, seek additional guidance or escalate the issue if necessary. Your hosting provider’s support team should assist you in finding a resolution that ensures seamless communication with Cloudflare. 


Resolving Error 521 when using WordPress with Cloudflare requires a systematic approach to address potential connectivity issues between Cloudflare’s edge servers and the origin server hosting your website. 

Ultimately, a proactive and collaborative approach is key to maintaining a stable and reliable WordPress website integrated with Cloudflare services. 

What is Error 521?

Error 521 is an HTTP status code that indicates a server-side issue where Cloudflare is unable to make a TCP connection to the origin web server. This error occurs when the origin server refuses the connection from Cloudflare, leading to a downtime of the website. 

Why am I seeing Error 521 on my WordPress site?

You may encounter Error 521 on your WordPress site due to various reasons, such as: 
Origin server downtime or unavailability. 
Firewall restrictions block Cloudflare’s IP addresses. 
Network connectivity issues between Cloudflare and the origin server. 
SSL/TLS certificate mismatches. 
Misconfigurations on the origin server or Cloudflare settings.

What steps can I take to fix Error 521 on my WordPress site?

To address Error 521 on your WordPress site, you can take the following steps: 
Verify the availability of your origin server. 
Whitelist Cloudflare’s IP addresses on your server. 
Ensure that port 443 is enabled for secure HTTPS connections. 
Create and upload a Cloudflare Origin Certificate. 
Review and adjust firewall settings on your server. 
Check DNS settings and resolve any issues. 
Monitor server logs for errors and network connectivity problems.

How do I diagnose the cause of Error 521?

To diagnose the cause of Error 521, you can: 
Verify server uptime and accessibility. 
Review server logs for error messages. 
Test network connectivity using diagnostic tools. 
Check firewall settings and whitelist Cloudflare’s IP addresses. 
Ensure that SSL/TLS certificates are correctly configured. 
Investigate any recent changes to the server or Cloudflare settings.

Are there any specific Cloudflare settings I should check to resolve Error 521?

To troubleshoot and resolve Error 521 with Cloudflare, you should: 
Review your DNS settings to ensure they are correctly configured. 
Check SSL/TLS settings and confirm certificate compatibility. 
Verify that firewall rules do not block Cloudflare’s IP addresses. 
Monitor Cloudflare Traffic and Security settings for any anomalies. 
Configure Page Rules or other settings that may impact the connection to your origin server.