Http 520 ошибка

Ошибки 520, 521, 522, 524 могут появляться на сайте в том случае, если вы используете для своего сайта сервисы Cloudflare. Cloudflare — сервис, перенаправляющий трафик. Он позволяет увеличить скорость загрузки сайта и обеспечивает защиту от хакерских и DDoS-атак.

Ошибка 520 (Web server is returning an unknown error)

Если Cloudflare не удается обработать ответ сервера, на котором размещен сайт, то он выдает эту ошибку.

Причины появления ошибки 520

1. Разрыв соединения, когда запрос к серверу был успешным.
2. Превышение размера заголовка запроса (больше 8 КБ).
3. Ответ сервера не содержит информацию.
4. Ответ сервера некорректен.

Способы устранения ошибки 520 Web server is returning an unknown error

Если любое из вышеперечисленных условий исходит от веб-сервера, на котором размещен сайт, нужно обратиться в техподдержку хостинг-провайдера.

Правила ограничения скорости Cloudflare или другие запросы фильтрации иногда могут вызывать проблемы в работе сайта. Важно проверить и протестировать ваш сайт после подключения сервисов Cloudflare. Если на сервере хостинга используются системы безопасности, блокирующие запросы к сайту, обязательно укажите IP-адреса Cloudflare в белом списке, чтобы исключить вероятность блокировки запросов.

Список диапазонов IP-адресов Cloudflare

Ошибка 521 (Web Server Is Down)

Браузер показывает ошибку 521, когда веб-сервер неожиданно обрывает соединение с Cloudflare.

Причины появления ошибки 521

1. Невозможно получить ответ от сервера.
2. Система безопасности веб-сервера внесла запросы Cloudflare в черный список. Это связано с тем, что система работает по принципу обратного прокси-сервера. Ваша система безопасности могла принять периодические подключения от статических IP-адресов за DDoS-атаку. Из-за этого адреса блокируются или ограничиваются по скорости.

Способы устранения ошибки 521 Web Server Is Down

Возможно, веб-сервер отключен или работает с перебоями. В таком случае:

1. Убедитесь, что ваш веб-сервер работает нормально.
2. Просмотрите журналы ошибок сервера, чтобы выявить причину ошибки.

Если веб-сервер или хостинг-провайдер блокируют запросы Cloudflare, внесите в белый список все диапазоны IP-адресов сервиса в брандмауэре сервера или другом программном обеспечении безопасности.

Ошибка 522 (Connection timed out)

Появляется в случае, когда превышено время ожидания ответа от веб-сервера.

Причины появления ошибки 522

1. Веб-сервер не может ответить на запрос из-за высокой загруженности.
2. Система защиты веб-сервера блокирует запросы Cloudflare.
3. Нет доступа к веб-серверу.

4. Некорректно указаны настройки DNS на Cloudflare: запросы отправляются по другому адресу.

5. Неверная настройка маршрутизации между Cloudflare и веб-сервером.

Способы устранения ошибки 522 Connection timed out

Убедитесь, что:

  Туториал: как исправить ошибки сервера

Ошибки 520, 521, 522, 524 связаны с проблемами в работе сервиса CloudFlare.

CloudFlare — сервис для перенаправления трафика на сайт с помощью облачного прокси-сервера, который обеспечивает дополнительную защиту от DDoS-атак и ускоряет загрузку вашего сайта.

Ошибка 520 Unknown Error

Что означает ошибка 520? Система CloudFlare выдает 520 ошибку, если не может обработать ответ от веб-сервера, на котором расположен сайт:

Причины появления ошибки:

• сброс соединения (после успешного запроса сервер разорвал соединение);
• заголовок запроса превышает ограничение размера заголовка Cloudflare (более 8 КБ). Если у вас много файлов cookie или они очень большие, это может привести к увеличению размера заголовков. Так как у Cloudflare есть ограничение на размер заголовка в 8 КБ, он не может обработать длинный заголовок;
• пустой ответ от сервера. Это происходит, когда DNS домена указывают на неправильный сервер.
• некорректный ответ от сервера;
• система безопасности блокирует запросы. Укажите IP-адреса Cloudflare в белом списке, чтобы система не блокировала запросы.

Способы устранения ошибки:

1. Отключить CloudFlare. Так вы сможете понять, где находится ошибка (на сервере или в CloudFlare).
2. Удалить плагины. Для плагинов иногда требуется много файлов cookies. Если на сайте много плагинов, это может повлиять на размер заголовков. Они могут быть слишком большими по размеру, и Cloudflare не справится с ними. Чтобы исправить ошибку, отключите плагины один за другим. Если ошибка пропадёт, удалите некоторые из плагинов.
3. Проверьте настройки DNS в CloudFlare. Убедитесь, что запись A указывает на правильный IP-адрес.

Подробные рекомендации по исправлению ошибки 520 даны в справке CloudFlare.

Ошибка 521 Web Server Is Down

Код ошибки 521 возникает, когда веб-сервер обрывает соединение с CloudFlare:

Это может произойти в двух случаях:

• сервер не отвечает или недоступен. Необходимо проверить работоспособность сервера;
• веб-сервер блокирует запросы CloudFlare. Поскольку CloudFlare работает как обратный прокси-сервер, все запросы к серверам поступают от IP-адресов CloudFlare. Иногда система безопасности хостинга принимает постоянные подключения с одних и тех же IP-адресов за DDoS-атаку. В результате на IP-адреса CloudFlare накладывается блокировка/ограничения по скорости.

Диапазон IP-адресов CloudFlare вы можете увидеть по ссылке.

Рекомендации по исправлению ошибки 521 даны в справке CloudFlare.

Ошибка 522 Connection timed out

Ошибка 522 возникает, если превышено время ожидания ответа от веб-сервера и пользователь не может попасть на страницу:

Основные причины:

• веб-сервер перегружен и не ответил на запрос,
• на веб-сервере стоит система защиты, которая блокирует запросы от CloudFlare,
• веб-сервер недоступен,
• некорректный IP-адрес, установленный в настройках DNS на CloudFlare (Запрос от CloudFlare был отправлен на другой IP),
• проблемы с маршрутизацией сети между CloudFlare и веб-сервером.

Что делать? Для решения проблемы удостоверьтесь, что ваш веб-сервер активен и принимает HTTP-запросы. Проверьте, корректны ли настройки DNS в личном кабинете на CloudFlare.

Подробные рекомендации по исправлению ошибки 522 даны в справке CloudFlare.

Как исправить ошибку 522 в Google Chrome

Методы решения:

1. Очистите кеш браузера. Браузер может быть переполнен данными о посещении сайтов. Освободите место в кэше браузера по инструкции.
2. Удалите расширение браузера, которое нарушает соединение с сервером. Отключайте расширения по очереди, чтобы найти то, которое выдает ошибку.
3. Проверьте подключение к интернету. Низкая скорость интернета или перебои при подключении может повлиять на время получения ответа сервера. Из-за этого и появляется ошибка 522.

4. Очистите кеш DNS. Проблемы с соединением могут возникнуть из-за несоответствия IP-адреса сервера сайта в кэше компьютера с реальным адресом. Такое происходит, когда владельцы сайтов по какой-либо причине меняют IP-адреса сервера. Чтобы устранить эту проблему, воспользуйтесь инструкцией.

Ошибка 524 A timeout occurred

Ошибка 524 возникает, когда подключение с веб-сервером установлено, но он не ответил за установленное время ожидания соединения:

Время ожидания HTTP-ответа на CloudFlare — 100 секунд. Если веб-сервер не предоставил ответ, система выдаст 524 ошибку.

Основные причины:

• длительная работа PHP-процесса или запроса к базе данных;
• веб-сервер перегружен. Проверьте доступные ресурсы сервера, в том числе процессор и оперативную память.

Если вы регулярно выполняете тяжелые запросы, которые могут занять больше 100 секунд, переместите эти процессы на субдомен, который не проксимируется в Cloudflare.

Рекомендации по исправлению ошибки 524 даны в справке CloudFlare.

Ошибки 520-524 требуют много знаний о сервере и его работе, поэтому самый верный способ решить проблему ― обратиться к хостинг-провайдеру, администратору сайта или к технической поддержке CloudFlare (если проблема на стороне их сервиса).

Introduction

Cloudflare’s error 520 is a complex error code indicating that a webpage cannot be reached. The complexity of the issue lies in the variety of reasons that could have caused it.

Becoming familiar with potential causes is the key to streamlining the troubleshooting process.

This article explains what the error means, why it occurs, and how to troubleshoot and resolve it.

Error 520 is a Cloudflare error message indicating that the origin web server received an invalid or incorrectly interpreted request, resulting in an empty response. 

What Causes Error 520?

The most common causes for error 520 are:

• PHP applications crashing.
• Incorrectly configured DNS records.
• Corrupt or incorrectly configured .htaccess file.
• Large request headers and excessive cookie usage.
• Missing request headers.
• Empty response from server.

How to Troubleshoot and Fix Error 520

The following steps outline the process of investigating the cause behind Cloudflare’s error 520, so appropriate action can be taken accordingly.

1. Pause Cloudflare

If the issue lies in Cloudflare, pausing it will make the page affected by the error accessible again. 

To pause Cloudflare: 

1. Log in to your Cloudflare account. 
2. Navigate to the Overview tab in the left-hand panel.
3. Scroll down to the Advanced Actions section and select Pause Cloudflare on Site. 

2. Check DNS Records

Domain Name System (DNS) records are files in authoritative DNS servers that specify: 

• What IP address is associated with a domain. 
• How to handle incoming requests for that domain. 

For Cloudflare to work properly, Cloudflare DNS records must match the ones in the domain’s DNS management system. 

To locate Cloudflare’s DNS records for a website: 

1. Log in to Cloudflare.
2. Select the website that outputs the error 520.
3. In the left-hand menu, select DNS > Records.

The exact steps to access a domain’s DNS settings depend on the website’s hosting platform. 

3. Restart PHP

Error 520 occurs also when a PHP application crashes. In that case, restarting the web server hosting the website fixes the issue. 

Depending on your software stack, PHP can be restarted in several ways. Below are instructions on how to restart an Apache or Nginx server on different operating systems.

Apache Web Server

To restart an Apache server running on an Ubuntu or Debian system, run:

sudo systemctl restart apache2

To restart an Apache server running on a CentOS 7 system, run:

sudo apachectl -k restart

Nginx Web Server

To restart an Nginx server gracefully, run:

sudo systemctl reload nginx

To force restart an Nginx server, run:

sudo systemctl restart nginx

Alternatively, to force close and restart Nginx and related processes, use:

sudo /etc/init.d/nginx restart

Some hosting platforms allow users to restart PHP using a graphical user interface (GUI). In that case, consult the hosting platform’s user manual or contact the customer support department. 

4. Check Headers and Cookies

The maximum allowed size of Cloudflare’s request headers is 32 KB, 16 KB per individual header. Exceeding these thresholds may cause the 520 error to occur. 

Information regarding the request headers’ size is available in the origin server’s HAR (HTTP Archive) file. 

To generate and extract a HAR file using Google Chrome:

1. Open the web page displaying the 520 error.
2. Right-click and select Inspect.

1. Select the Network tab.
2. Check the Preserve log option.
3. Click the Clear (stop sign) button.

1. Reload the page.
2. Right-click anywhere in the area below the nav bars of the inspect tool.
3. Select Save all as HAR with content.

The process of generating a HAR file is almost identical between different major web browsers since they are all built upon Chromium (except Firefox).

Examining HAR files is only possible with software like Google’s HAR Analyzer. 

The anomaly to look for in HAR files is cookies that are too large and the overall excessive use of cookies.

To reduce cookie size and lighten the request header load:

• Remove unnecessary third-party plugins from the website.
• Limit request overhead.
• Use a cookie-free domain.

5. Disable .htaccess

The .htaccess file affects the global configuration of an Apache server without changing the configuration files.

Error 520 can appear when a redirect was not configured properly in the .htaccess file, or the file itself is corrupted. Disabling the .htaccess file will reveal whether the file is problematic.

1. To disable the .htaccess file, start by opening the apache2.conf file in a text editor (we are using nano):

sudo nano /etc/apache2/apache2.conf

The default location for the Apache config file is one of the following:

• /etc/httpd/httpd.conf
• /etc/apache2/httpd.conf
• /etc/apache2/apache2.conf
• /etc/httpd/conf/httpd.conf

2. Find the value of the AllowOverride directive and change it to None.

<Directory /var/www/html>
        Options Indexes FollowSymLinks MultiViews
        AllowOverride None
        Require all granted
</Directory>

3. Save and close the file.

4. To apply the changes, restart Apache:

sudo systemctl apache2 restart

6. Check Web Server Error Logs

Error logs provide additional information about where, why, and what error occurred. 

The process of locating or generating error logs varies between hosting providers. However, all error logs feature a similar structure and will provide the following information:

• The date and time of the incident.
• The IP address of the client (if the client caused the error to happen).
• An error message.
• A path to the affected resource or the line of code causing the issue.

7. Check HTTP Error Response with a cURL Command

Client URL (cURL) commands allow users to get information about the HTTP error response code and request headers.

The general syntax is:

sudo curl -svo /dev/null https://yourwebsitehere.com

A successful response will look like the following example:

*   Trying 111.11.1.111...
* Connected to 111.11.1.111 (111.11.1.111) port 100 (#0)
> GET /login HTTP/1.1
> User-Agent: YourBrowser 1.0
> Accept: */*
> Host: examplewebsite.com
>
< HTTP/1.1 200 OK
< Content-Type: text/html
< Date: Day, DD, Month Year Hour:Minute:Second Timezone
{ [11111 bytes data]
* Connection #0 to host 111.11.1.111 left intact

However, the command will not be able to retrieve information if the 520 error has occurred, and the result will look similar to the following example:

*   Trying 111.11.1.111...
* Connected to 111.11.1.111 (111.11.1.111) port 100 (#0)
> GET /login HTTP/1.1
> User-Agent: YourBrowser 1.0
> Accept: */*
> Host: examplewebsite.com
>
* Empty reply from server
* Connection #0 to host 111.11.1.111 left intact

8. Contact Cloudflare Support

If none of the previous methods helped locate the source of the issue, contacting Cloudflare support is the next step.

Cloudflare offers two support methods:

• Support tickets – available to all accounts and accessible via the admin dashboard.
• Live chat – available to Business and Enterprise accounts only.

In both cases, representatives will request the following information:

• URL(s) of the affected resource(s)
• Cloudflare’s Ray ID from the affected resource(s)
• The result of entering the following URL in a browser http://example.com/cdn-cgi/trace (replace example.com with the right domain)
• A HAR file from when Cloudflare was enabled on the website
• A HAR file from when Cloudflare was disabled on the website

Conclusion

Discovering and resolving errors quickly is paramount to reducing downtimes and ensuring positive user experiences.

Use the information in this guide to prevent, troubleshoot, and resolve 520 errors.

Besides error 520, websites using Cloudflare’s CDN can display a variety of other error messages, a common one being 521: Web server is down. Read our guide to find out what error 521, 504 Gateway Timeout or 526 Invalid SSL Certificate error means and how to troubleshoot and fix it.

When your site’s visitors see error 520 in their browser, it means Cloudflare is sending the message because your server returned an empty, unknown, or unexpected response.

The 520 error can be approached through troubleshooting first to find the cause and then fixed following these steps.

Let’s jump right in.

Troubleshooting Error 520

Since the 520 error is coming up because of an issue on your server, you can troubleshoot the issue by looking in your error log.

Disable Cloudflare

Before you start troubleshooting, it’s necessary to disable Cloudflare. This helps isolate the problem by ensuring the issue can be replicated without Cloudflare being a factor.

Step 1

Start by logging into Cloudflare. Then, find your site on the list and click on it.

Step 2

Next, click on the DNS tab, then on the orange cloud under the Proxy status section in the table. You’ll know Cloudflare was disabled because the cloud will have turned gray.

Pause Cloudflare

Alternatively, you can choose to pause Cloudflare after logging in.

Step 1

Click on your connected site from the list.

Step 2

Then, scroll down until you see the Advanced Actions section in the sidebar. Click on the Pause Cloudflare on Site link.

Step 3

A pop-up will be displayed on the page that asks you to confirm you want to pause Cloudflare. Go ahead and click the Confirm button.

Go into Development Mode

If you don’t want to pause or disable Cloudflare, you can keep it running, but place it in development mode so you can still troubleshoot error 520.

Step 1

After logging into Cloudflare, click the Caching tab toward the top of the page.

Step2

Next, scroll down to the Development Mode section and click the Off toggle button. It should now say “On.”

Checking Your Server’s Error Logs

Now that you have disabled, paused or put Cloudflare into development mode, you can troubleshoot error 520 by checking your server’s error logs.

Finding your error log can vary between hosts so check with yours if you’re unsure of where to find your error logs.

If your hosting provider uses cPanel, you can follow the steps below.

Step 1

Log into cPanel and in the dashboard, go to the Metrics section. Then, click the Errors button.

Step 2

The error log page displays errors in reverse chronological order as well as up to 300 of the most recent messages. The error log may display more messages if you or your host adjusted the settings.

Checking Your Log for Error 520 Using MyKinsta

If you host your WordPress site with Kinsta, you can follow the steps below to check your error log.

Step 1

Log into MyKinsta and click on Sites in the menu on the left. Then, select the site you want to troubleshoot from the list on the page.

Step 2

Click on the Logs tab. By default, the error log is displayed. If you don’t see anything listed, it’s due to the fact that no errors on your site have occurred.

How to Interpret the Error Log

Each message in an error log has a structure. If you understand it, you can interpret the error messages that come up.

[Fri Oct 11 17:00:30 2019] [error] [client 123.4.56.7] error description: /path/to/file/with/error

The date and time of the message are listed first followed by the LogLevel directive which tells you about the severity level of the message.

Next up is the IP address of the client. This is who made the issue appear.

Finally, the actual message is displayed and may contain a path to the affected file.

Here are the LogLevel severity levels which could be listed in your error log’s messages:

• Emerg – This lets you know the issue is an emergency and the server is unavailable.
• Alert – Action should be taken immediately if you see this level.
• Crit – This denotes a critical condition.
• Error – This means an error has occurred.
• Warn – A message with this level is a warning about an issue that requires your attention, but isn’t critical.
• Notice – This means your server is normal, but there are significant details about the condition of your server that is available.
• Info – General information is available with this level.
• Debug – These messages contain details when you have debugging enabled.

Use a cURL Command to Troubleshoot Error 520

You can also use a cURL command to troubleshoot error 520 by testing against the origin server.

curl -vso /dev/null --user-agent "Mozilla 5.0" -H "Host: your-site.com" http://123.45.6.789/wp-login.php

Be sure to change “you-site.com” to your actual domain. You also need to update “123.45.6.789” with your site’s IP address. If you changed your login page, you should also change the “wp-login.php” part.

A successful response header would look similar to the example below:

* Hostname was NOT found in DNS cache
*   Trying 123.45.6.789...
* Connected to 123.45.6.789 (123.45.6.789) port 80 (#0)
> GET /login HTTP/1.1
> User-Agent: Mozilla 5.0
> Accept: */*
> Host: your-site.com
>
< HTTP/1.1 200 OK
< Content-Type: text/html
< Date: Day, DD, Month Year Hour:Minute:Second Timezone
{ [12345 bytes data]
* Connection #0 to host 123.45.6.789 left intact

If you see something like this, it means everything’s okay and the site was reached without an error 520 response.

On the other hand, if you see a response header similar to the example below, it means the 520 error has occurred when Cloudflare was active:

* Hostname was NOT found in DNS cache
*   Trying 123.45.6.789...
* Connected to 123.45.6.789 (123.45.6.789) port 80 (#0)
> GET /login HTTP/1.1
> User-Agent: Mozilla 5.0
> Accept: */*
> Host: your-site.com
>
* Empty reply from server
* Connection #0 to host 123.45.6.789 left intact

How to Generate a HAR File

A HAR is an HTTP archive file. It contains archives for requests that are going to the server of origin and also through Cloudflare.

It can help you with troubleshooting because it compares response headers coming from the origin server and Cloudflare when it’s used as a proxy.

It’s also used to confirm that the headers are too large if that’s why error 520 has appeared.

You can create a HAR file with your browser with the steps below:

Chrome

Step 1

Open your browser and right-click on the page. Then, select Inspect.

Step 2

Once the panel has opened, click the Network tab and make sure there’s a red circle button toward the top, left-hand side of the panel. If it’s gray, click it.

Step 3

Check the Preserve log option next to the record button and then click the clear button.

Step 4

Load the page that’s bringing up error 520. Then, right-click anywhere in the messages area of the Chrome developer tool.

Select the Save as HAR with Content and save the file to your computer.

Firefox

Step 1

Open Firefox and right-click anywhere on the page. Then, select Inspect Element.

Step 2

Go to the Network tab and visit the page that has the 520 error coming up. Right-click on messages in the panel and select the Save All as HAR option.

Save the file to your computer.

Edge

Step 1

Open the Edge browser and right-click the page. Select Inspect from the list.

Step 2

Go to the Network tab and ensure the circular record button is red. If it’s not, click it. Check the Preserve log option, then the icon to clear the current messages.

Step 3

Go to the page where you’re experiencing error 520. Then, right-click on the messages in the developer tool panel and select the Save all as HAR with content option.

Save the file to your computer.

Safari

Step 1

Open Safari and right-click on the page for Windows or press CMD on your keyboard and click for Mac. Select Inspect Element from the list.

Step 2

Go to the Network tab. Check the Preserve Log option, then go to the page with the error 520 issue.

Step 3

Click the Export button and save the HAR file to your computer.

Resolving the Common Reasons for Error 520

Now that you have your error log, search through it and see if you notice any one of the issues below. Then, follow the steps below to resolve the issue.

Origin Server PHP Application Crashed

One common issue that causes error 520 is that one of the PHP applications have crashed on your server. Restarting PHP will fix the error.

Step 1

Using SSH, you can enter the command below for Apache servers:

apache2ctl restart

For Nginx servers, you can restart PHP using the command below:

service nginx restart

Restart PHP in MyKinsta

If your site is hosted with Kinsta, you can restart PHP in a few clicks.

Step 1

Log into MyKinsta and click on Sites on the left. Then, click on your site from the list.

Step 2

Go to the Tools tab and click the Restart PHP button.

Cloudflare IP Addresses Aren’t Whitelisted

Another reason why the 520 error can occur is if Cloudflare’s IP addresses aren’t whitelisted. You can whitelist them, but the steps vary between hosting providers.

If you’re not sure how to whitelist IPs, contact your host, especially if you don’t find any settings for it.

At Kinsta, Cloudflare’s IP addresses are whitelisted by default so there’s no need to worry about this cause of the error. It also won’t impact the other reasons why the error occurs.

TCP Idle Timeouts Are Shorter Than 300 Seconds

The Transmission Control Protocol (TCP) could also be the cause of error 520.

TCP is a standard protocol that establishes and maintains a network connection. If the TCP is set to timeout in under 300 seconds, it could cause the 520 error to pop up.

You can change the TCP service timeout using a CLI command:

set service Service-HTTP-1 -svrTimeout 500

Headers Exceed 8 KB

This issue is typically due to too many cookies or cookies that are too large. The HAR file that you downloaded during the troubleshooting process will show you if this is the problem.

Cloudflare has a limit of 8 KB that can be used for headers.

If you authored a plugin that requires too many cookies or has too much data in its cookies, try to reduce them. Or, if you’re using a lot of plugins that all need cookies, remove some of them (you should always use quality plugins).

Elementor Users

When you try to edit your WordPress site using Elementor and you get the 520 error – “Web server is returning an unknown error” – you can check the following.

First, you can try a different web browser.

If the problem still exists and your site is behind Cloudflare you may have a problem with Cloudflare’s Rocket Loader feature.

The issue was caused by Rocket Loader automatically changing the scripts to load asynchronously, which breaks the site editor and prevents you making changes.
By creating rules in Cloudflare you can solve this issue.

For Elementor pages: Site URL/*elementor*
For Elementor templates: Site URL/?elementor_library=*

Empty Response from Your Server

This problem occurs when your site lacks an HTTP status code or response body. To resolve it, make sure your DNS settings are set correctly for your site’s domain.

The steps involved to check your settings depends on your DNS host. If your hosting plan has DNS bundled with it, then check with your hosting provider.

It may be important to note that if you updated your DNS settings, it may take up to 72 hours for your site to propagate. This means your site may be unavailable for up to three days.

After changing your DNS settings, you need to clear your site’s cache. If you have a caching plugin installed on your WordPress site, you can check its documentation if you’re unsure of how to clear your site’s cache from the plugin’s settings.

You can also clear your site’s cache through your hosting provider. Be sure to check with them if you need to know how to do this for your site.

If your site is hosted with Kinsta, you can click Sites in the menu, then on your listed site.

Then, click the Tools tab and click the Clear cache button.

If you have updated your DNS settings, your site is available again, you cleared your site’s cache and you still are experiencing error 520, restart your server.

If you don’t find the option in your settings, contact Kinsta’s support team and we’ll help you with this.

Missing Response Headers

According to Mozilla,

“A response header is an HTTP header that can be used in an HTTP response and that doesn’t relate to the content of the message. Response headers, like Age, Location or Server are used to give a more detailed context of the response.”

Missing response headers can be caused by a multitude of reasons.

Your best bet with this issue is to use a debugging tool like Fiddler to debug the issue and see exactly what the problem is so you can fix it.

Server not Returning Proper HTTP Error Responses

When your server sent an invalid error response, it could have caused the 520 error. This means the message didn’t fit in with the standard list of HTTP response codes.

It’s caused by your server or it could also be something on your server such as PHP applications or possibly plugins used on your WordPress site.

If you can’t find the source for the improper error code to fix it, try contacting support for further help.

Enabling Cloudflare Again

Check to see if you receive the error again. If you do, keep Cloudflare disabled and continue troubleshooting.

If the 520 error has been resolved, enable Cloudflare again.

Step 1

To do this, log into Cloudflare and if you disabled Cloudflare by turning the cloud gray in your account, start by selecting your site from the list.

Step 2

Click the DNS tab, then click the gray cloud to re-enable Cloudflare.

Restoring Cloudflare After Pausing It

Step 1

If you paused Cloudflare earlier, restore it by logging into Cloudflare and click on your listed site in the dashboard.

Step 2

Then, go to the Overview tab and scroll down to the bottom of the page until you see the Advanced Actions sections in the sidebar on the right-hand side of the page.

Click the Enable Cloudflare on Site link.

Turning off Development Mode

Step 1

If you have previously turned on Cloudflare’s development mode, you can turn it off by logging in. Then, click your site that’s listed on the page.

Step 2

Next, go to the Caching tab.

Step 3

Scroll down to the Development Mode section and click the toggle button that’s currently set to “On.”

What to Do If All Else Fails

If you’re still seeing issues, contact Cloudflare support.

Provide them with the following details:

• Full URL(s) of the requested resource when the error occurred.
• Cloudflare’s Ray ID from the page where you saw the error 520 message.
• The output from http://your-site.com/cdn-cgi/trace, but be sure to replace “your-site.com” with your actual domain name.
• Two HAR files: One from when Cloudflare was enabled for your site and one more from when you had Cloudflare disabled.

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Summary

The 520 error can seem confusing, especially since it’s a Cloudflare error. But, it has to do with an error with your server that causes Cloudflare to not connect.

The steps above are the solutions to the most common causes of error 520. If you’re still having issues after trying them, you might want to contact Cloudflare or your hosting support.

Suggested reading: How to Set up Cloudflare APO for WordPress.

HTTP response status code 520 Web server is returning an unknown error is an unofficial server error that is specific to Cloudflare. This is a catch-all error that is used in the absence of having a HTTP status code for one that is more specific.

Usage

Cloudflare is a content delivery network that acts as a gateway between a user and a website server. When the 520 Web server is returning an unknown error status code is received, it can mean one of several things:

• It can indicate that something unexpected happened with the origin server.

• The origin server incorrectly interprets the HTTP request.

• The origin server is unwilling to process the HTTP request due to a HTTP protocol violation or an empty response.

Takeaway

The 520 Web server is returning an unknown error status code is a Cloudflare-specific server error that is generated because the origin server response is empty, unknown, or unexpected.

See also

• Troubleshooting Cloudflare 520 Error