You have likely encountered an error message called Error code 521 if you use Cloudflare and have a WordPress website. For website developers and owners, nothing is more annoying than seeing error warnings. When attempting to access your WordPress website, Error 521 appears, and debugging might be rather difficult.
There are several reasons why this error might appear, from something as basic as a server overload to issues with your hosting company. Many website owners and end users frequently run into the 521 error code when they are browsing the internet. If left unresolved, it may have a detrimental effect on the user experience and web performance for website owners.
So, keep reading and exploring to learn what HTTP error 521 is and how to fix it professionally in 2025.
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What is Error Code 521?
Usually, error 521 happens when the web server is unable to establish a connection with your hosting provider. This kind of issue may be really annoying and have an impact on how well your website works.
Error 521 only happens on Cloudflare-enabled websites. The issue arises when a server timeout prevents the platform from connecting to the website’s original web servers.
Although you might believe that Cloudflare is to fault, the 521 error, or “Cloudflare encountered an error processing this request: internal server error,” is really the result of a problem with the server that hosts your website.
Yes, you are the issue!
Visitors to your website can contact Cloudflare’s server when this problem occurs, but Cloudflare cannot reach your server. Let’s now discuss what causes the Error code 521 to happen.
What Leads To Cloudflare And WordPress 521 Error Code?
Cloudflare Error 521 can occur for several reasons, including:
- Downtime of the origin server: Cloudflare’s edge servers won’t be able to connect if the origin server that hosts your website is unavailable or down, which will cause HTTP error 521.
- Firewall restrictions: Error 521 may occasionally occur when inbound connections from Cloudflare’s networking IP addresses are blocked by stringent firewall rules or security settings on the origin server.
- Problems with the origin server’s configuration: Inaccurate server settings, IP address limitations, or network setups can all hinder Cloudflare’s ability to connect and result in Error 521.
- Traffic overload: Unexpected increases in traffic or a heavy server load may cause the origin server to become overloaded, which will stop it from reacting to Cloudflare requests and cause a 521 error code.
- DNS resolution issues: Error 521 may arise when Cloudflare is unable to reach the origin server due to DNS resolution issues, such as improper DNS settings or delays in DNS propagation.
- SSL/TLS certificate mismatch: The handshake will fail, and Error 521 will be raised if the SSL/TLS certificate present on the origin server does not match the configurations set up in Cloudflare.
Communication breakdowns and a web server is down error code 521 might result from difficulties with routing or network connectivity between Cloudflare’s edge servers and the origin server.
Also Read: Error Code 524: A Complete Guide To Troubleshooting
How to Fix Error Code 521? Step-By-Step Guide
Now is the time to discuss how you can fix the Cloudflare encountered an error processing this request: bad gateway. Here are the steps you must follow to fix the HTTP error 521:
Speak With Your Hosting Provider
When a 521 error occurs, there are measures you may take to resolve the issue on your own. Some of them, meanwhile, can be complex and time-consuming.
That being said, getting in touch with your WordPress hosting provider is the simplest method to resolve an HTTP error 521. An excellent web host ought to be able to explain the cause of this problem. They could even help you resolve the issue.
Go to the website of your hosting provider if you don’t know how to get in touch with help. After that, you may search for any Support or Contact Us pages.
We advise using live assistance options when they are offered in order to assist you in resolving this issue as soon as feasible. For instance, corporate phone assistance or live chat is nearly always quicker than email or ticketing systems.
You might attempt the following actions if you are unable to contact your hosting provider, such as Temok Technologies, for assistance immediately.
Here’s a summary of how to approach this issue successfully:
Find the Root Cause
Before contacting your hosting provider, verify that port 443—the source of Error code 521—is disabled on your server. Enabling port 443—which is required for HTTPS connections—will help to create secure channels of communication.
Speak With Customer Service
Use live chat, email, or phone support to get in touch with your hosting provider’s support staff. Give a detailed explanation of the problem with Error 521 and ask for assistance in activating port 443 on your server.
Give Server Information
Share pertinent server details with your hosting provider when you get in touch with them, including the operating system, server settings, and server type (such as Nginx or Apache). The support staff will be better able to activate port 443 on your server with this information.
Make A Port Activation Request
Make sure your server has port 443 enabled in order to support secure HTTPS communications. Emphasize that in order to fix Error 521 and guarantee safe data transfer between Cloudflare and your server, port 443 must be enabled.
Confirm The Activation
Verify that port 443 is open for HTTPS communication after your hosting provider has enabled it. Check port 443’s availability for safe communication using network diagnostic tools or commands.
Look For Connection
Once you have opened port 443, check the Cloudflare connection by sending HTTPS requests to your origin server. Using internet resources or analyzing network logs, make sure HTTPS traffic is successfully reaching your server. This will show that port 443 activation has fixed Error 521.
Also Read: Error Code 520: Expert Advice To Resolve And Prevent It
Verify The Server Connection
The warning “Web server is down Error Code 521” will appear if the firewall software on your server bans Cloudflare IP addresses. Making sure your hosting provider hasn’t set rate-limiting IP requests from Cloudflare’s IP ranges is another way to resolve “Error 521.”
All connections to your server originate from Cloudflare’s Internet Protocol (IP) address instead of the actual one of your visitor because this CDN functions as a reverse proxy. A client Uniform Resource Locator (cURL) command can be used to verify the server and connection of the URL. By default, Windows 10 or later, Linux, and macOS all come with the cURL command installed.
Verify Your SSL Certificate
SSL certificate problems might also be the cause of the Error 521 notice. Verify that HTTPS is configured correctly and that your SSL certificate is installed.
Next, briefly turn off HTTPS redirection. The HTTPS reroute may have been the reason for the error 521 message if it vanishes.
Note: Get assistance from your hosting provider if you need assistance verifying your SSL certificate in the backend.
Add Every Cloudflare IP Address To Your Whitelist
Whitelisting Cloudflare’s IP addresses on your server is necessary for resolving Cloudflare 521 error and ensuring smooth interaction between your origin server and the edge servers of Cloudflare.
Obtain The IP Ranges For Cloudflare
A list of IP address ranges that Cloudflare’s edge servers employ is provided. This list may be found in the Firewall or Network settings section of the Cloudflare dashboard. To whitelist all the pertinent addresses, make sure you have the most recent list of Cloudflare’s IP ranges.
View The Firewall Configurations On The Server
Log in to the control panel or terminal on your server to view the firewall settings to fix error code 521. Tools like Windows Firewall, Linux’s iptables, or a third-party firewall administration interface can be used.
Add Cloudflare IP Addresses To A Whitelist
To accept inbound connections from Cloudflare’s IP ranges, add rules. You may set up particular rules to permit the HTTP port 80 & HTTPS port 443 website traffic from Cloudflare’s IPs, depending on how your server is configured.
Verify Connection
Once you have added Cloudflare’s IP addresses to the whitelist:
- Check your origin server and Cloudflare’s edge servers’ connections.
- Using programs like cURL or internet services, transmit inquiries from Cloudflare’s network to your server, then verify that the connections have succeeded.
- Keep an eye on the server logs for any errors or stopped requests that could point to problems with the whitelisting setup.
Also Read: Fix “Windows Can’t Communicate With The Device or Resource” Error
Regularly Update IP Whitelists
Usually, as Cloudflare grows its network, it updates its IP address ranges. Staying connected with Cloudflare’s servers requires keeping abreast of these developments and adjusting your whitelist as necessary.
Establish a process to regularly check and update the whitelisted IP addresses to guarantee reliable and secure communication between your server and Cloudflare. IP address
Upgrade Your Hosting Plan
As previously said, if your WordPress website receives a lot of traffic, increasing your hosting can be the best course of action.
To handle heavy traffic, you should upgrade to the special dedicated servers package, Virtual Private Server (VPS), or Cloud Server (while at the same time providing enough server capacity for your website).
If Your Security Plugin Clashes With Cloudflare, Disable It
Security plugins can also cause the error code 521. Cloudflare may not be able to access your server if it conflicts with WordPress security plugins that include firewall functionality.
For instance, Wordfence and Cloudflare may clash. Thus, turn off WordPress security plugins for a while and see if it fixes the issue.
Turn Off Mod_Reqtimeout And Mod_Antiloris
The Apache HTTP server modules mod_antiloris and mod_reqtimeout restrict the number of connections from distinct IP addresses within a certain amount of time, therefore thwarting Slowloris Denial-of-Service (DoS) assaults.
As a reverse proxy, Cloudflare handles requests and routes them to the original server. A restricted range of IP addresses is used to accomplish this. When mod_antiloris and mod_reqtimeout are configured, all further attempts to connect from a Cloudflare IP address that exceeds the connection limit are met with lost packets.
Disabling and unloading the modules will fix the problem and allow Cloudflare to continue operating normally.
Conclusion
A methodical approach is necessary to resolve any possible connectivity difficulties between Cloudflare’s edge servers and the origin server hosting your website in order to fix Error code 521 while using WordPress with Cloudflare.
In the end, keeping a WordPress website integrated with Cloudflare services stable and dependable requires a proactive and cooperative approach.
Your origin server is not responding to Cloudflare’s requests if your website displays the “Cloudflare encountered an error processing this request: internal server error” notice. A server’s firewall or other security software that bans Cloudflare IPs is frequently the cause of “Error 521.”
FAQs (Frequently Asked Questions)
How To Fix 521 Error?
You must make sure your server is available and has proper configuration in order to resolve error code 521. Checking SSL/TLS settings, whitelisting Cloudflare’s IP addresses, and confirming server availability are important troubleshooting procedures.
What Does 521 Status Code Mean?
“Web server is down” is an HTTP error code 521 that shows that a website’s server is rejecting a Cloudflare connection request.
What Does The Code 521 Mean?
“Error 521: Web server is down” is typically indicated by the code 521 when utilizing Cloudflare as a reverse proxy or CDN. It indicates that although the origin server rejected the connection, Cloudflare’s servers were able to establish a connection with the domain of your website.
How Do I Fix A Cloudflare Error?
Some solutions for problems are checking the server health, verifying DNS records, and clearing the cache and cookies in your browser. It also includes briefly turning off Cloudflare to limit the trouble.