Web Server is Down (Error Code 521): Quick Solutions for Site Owners

A 521 error code means Cloudflare can't connect to the website's server. Visitors won't be able to access your online store, which can cause a host of issues for website owners. It impacts traffic, affects your reputation, and creates frustrated visitors.

The good news is that a 521 error message is fixable. Keep reading to learn why it happens, how to fix it, and steps to prevent 521 errors from occurring in the first place.

What is a 521 error?

A 521 error is a type of HTTP code status. It indicates that Cloudflare, a content delivery network (CDN) and reverse proxy cloud provider, isn't connecting to the server. Instead of loading the website, a 521 error will display a message like "Web server is down."

Cloudflare is one of the "middleman" services that helps visitors connect to your site faster. It creates a cache of your site and distributes it across multiple servers worldwide, allowing visitors to connect to the server nearest them.

Cloudflare also adds an extra layer of security to websites. It monitors traffic for potential threats, such as distributed denial-of-service (DDoS) attacks. When a threat is detected, Cloudflare blocks it.

Here's how Cloudflare works when someone visits your website:

• A visitor requests to see your website, and the request gets sent to Cloudflare.
• Cloudflare determines if it's a legitimate request. If it's authorized, Cloudflare will ask the web server for the site.
• The web server sends the site.
• The website is displayed on the visitor's device.

When a 521 error occurs, it means that Cloudflare was unable to communicate with the web server. The failed connection prevents the site from loading.

Common causes for a 521 error

A 521 error is usually caused by an offline origin server or blocked Cloudflare requests. Here's an overview of why 521 error messages happen:

• Origin server issues: The website's original server may go down due to excessive traffic or insufficient resources. Since Cloudflare can't get a response from an unresponsive server, it sends the 521 error.
• DNS misconfigurations: The Domain Name System (DNS) directs a website request to the correct server. If it has an incorrect setup, Cloudflare can't make requests and sends a 521 error message.
• Firewall blocking Cloudflare: All connections to your web server go through Cloudflare first, which gives them the same IP address. A firewall may detect large amounts of traffic from a single IP address and trigger a 521 error.
• SSL configuration issues. To operate, Cloudflare needs valid Secure Sockets Layer (SSL) certificates, which are used for site authentication and data encryption. If the SSL certificate expires or goes missing, it can result in a 521 error, as the connection fails.

5 ways to fix a 521 error

A site owner needs to fix a 521 error before it has a significant impact on traffic, sales, and other visitor interactions. Here are 5 ways to troubleshoot and fix the problem.

1. Confirm the origin server is operational

Check your website's server. You can do this through your web hosting service. Many providers have a control panel that includes server monitoring tools. These tools help flag whether the server is experiencing downtime, high traffic, or other issues — all of which impact Cloudflare functionality.

2. Check SSL settings

Review the encryption settings of your site hosting. You'll review the SSL/TLS settings to ensure proper configuration. Confirm that the SSL/TLS mode is set to Full or Full (Strict). The setting will create end-to-end encryption from the origin server to the visitor's browser.

Also, confirm that your origin server supports HTTPS. You may need to install a Cloudflare Origin Certificate, depending on the SSL/TLS mode that you choose.

3. Change firewall settings

The firewall may have blocked Cloudflare IPs; to allow them through the firewall, whitelist these IP addresses. Cloudflare publishes its IP Ranges, which you can compare to your hosting server.

In addition to the firewall, review other security protocols and plugins to see if they are blocking Cloudflare IPs.

4. Refer to server logs

Take a look at the error logs for the origin server. It tracks issues like connection failures, PHP errors, or code conflicts. You may find the error logs in the hosting's file manager or with FTP access.

Start by looking for crashes around the time that the 521 error occurred. This provides clues about what happened and how to respond.

5. Run direct connection diagnostics

Test to see if your website can run without Cloudflare. This step helps determine if the 521 error is coming from the web server or Cloudflare's connection.

The simplest method is pausing Cloudflare. Without Cloudflare, visitors go to your website directly. Here's how to do it:

1. Log in to your Cloudflare dashboard.
2. Go to the Account home page.
3. Select your account and domain name.
4. Within the Overview, choose Advanced Options.
5. Click Pause Cloudflare on Site.

If the site loads, it means that there is a Cloudflare or firewall problem. If the 521 error continues, the issue lies with the origin server.

Ways to prevent future 521 messages

Taking preventative measures to stop 521 messages can save you from future headaches. Here are four ways to maintain your site.

1. Monitor the origin server. Review uptime to ensure no significant issues. Use tools like UptimeRobot or Pingdom to track your site's uptime. You should also evaluate your traffic and memory space to see if you need to upgrade to a different web hosting type.
2. Adjust firewall rules. Whitelist all Cloudflare IPs to prevent firewalls from blocking them.
3. Keep DNS/SSL configurations updated. Keep the site's SSL/TLS certificate valid. If you move hosting providers, make sure that the DNS is configured correctly to prevent issues.
4. Choose a reliable host. Dependable web hosting providers are the gateway to a reliable website. Find a web hosting provider that keeps up with Cloudflare.

FAQs

Bottom line

A 521 error means a server is down or Cloudflare can't connect to it. Until the problem is fixed, visitors cannot reach your website. It can affect your website traffic, prevent sales, and cause a poor user experience.

You can address it by pausing Cloudflare to determine if it's the problem or if the issue is server-side. Then, review error logs for server issues, whitelist Cloudflare IP addresses, or execute other solutions.

Choosing a reliable web hosting provider is important to keep your site running. When comparing top web hosting providers, choose one that offers virtually no downtime and provides support for server issues.