If you have been a web developer or administrator then you must be familiar with the 503 Error Code. It is an internal server error. This error can occur on any web browser, operating system, or smartphone. The error majorly occurs with websites made on WordPress. If you have been using WordPress you must know about Jetpack. It is a very famous WordPress plugin that has over a million active installs. The plugin helps in remotely managing the WordPress.com interface to manage a stack of your WordPress blogs. The complexity arises when using varnish and Jetpack. And if you are using Varnish on your blog, you might get 503 Error Code Backend Fetch Failed.

503 Error Code

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Causes Of 503 Error Code Backend Fetch Failed

Since we know that the issues mainly occur because of using varnish and jetpack combo, there is not any one specific cause. Users who have faced this error differ when it comes to the causes of 503 Error Code Backend Fetch Failed. For example, some user claims that the error occurs because of insufficient memory, If the server does not have sufficient memory or if the requests are too many, the backend link to the server fails and the 503 Error Code appears. Also, when the Varnish cache is corrupted the error appears.

  • Insufficient Memory
  • Corrupted Varnish Cache
  • Incorrect Varnish Configuration
  • Insufficient Number of Headers in Varnish
  • WordPress Plugin issues

Similar Types Of 503 Error Code Backend Fetch Failed

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How to Fix 503 Error Code Problem Issue Quickly

Below we have demonstrated all the possible ways to fix 503 Error Code Backend Fetch Failed.

1. Increasing the Header Limit

In the first method, we will try to fix the 503 Error Code issue, by fixing the jetpack and varnish combination. If you are using both of them it is recommended to go with this method first. To fix the issue we have divided the solution into two parts.

A). Checking The Error

In the first part, we will find out the cause behind the 503 Error Code Backend Fetch Failed. Follow each step carefully.

  • STEP 1. To track the cause, open up an SSH session for your server with Varnish
  • STEP 2. While you are in the console, run the varnish log command
varnishlog -q "BereqHeader ~ '^Host: .*\.domain.com'" > bereq.log
  • STEP 3. The above command will track all the requests that happened in the background, and create a text file of it
  • STEP 4. The next thing you need to do is to Deactivate your Jetpack
  • STEP 5. After a few seconds activate it back again
  • STEP 6. You will see the below error in your browser
Error 503 Backend fetch failed
Backend fetch failed
Guru Meditation:
XID: 2230744
  • STEP 7. The important thing here is the XID code, kindly copy it someplace safe, we will be needing it in the future steps
  • STEP 8. Now get back to the console and press Ctrl + C, to close the varnish log command
  • STEP 9. Head to the log file you have generated by the name bereq.log
  • STEP 10. Open it and if you find the below information
-   BogoHeader     Too many headers: Set-Cookie: jetpackS
-   HttpGarbage    "HTTP/1.1%00"
-   BerespStatus   503
-   BerespReason   Service Unavailable
-   FetchError     http format error
  • STEP 11. If you get too many headers or similar then the error is with the headers, which is the major cause of Error 503 Backend Fetch Failed
  • STEP 12. Now let’s proceed to the next part to fix this issue

B. Fixing Too Many Header Issues

In the above part, we have tracked the issue this part is the resolution part of the issue. Follow each step carefully to fix the 503 Error Code issue. To fix the issue we have to tweak the header limit. The default header limit is 64 and we will change it to 96.

  • STEP 1. To fix the issues, head to the below location and locate the varnish configuration file
  • STEP 2. Once you find the file look for the text DAEMON_OPTSΒ 
  • STEP 3. And add the parameter for the number of HTTP headers
  • STEP 4. It should be like,
             -f ${VARNISH_VCL_CONF} \
             -p    http_max_hdr=96    \ #  this is the tuned parameter we added
             -p thread_pool_min=${VARNISH_MIN_THREADS} \
             -p thread_pool_max=${VARNISH_MAX_THREADS} \
  • STEP 5. Once done save the file and check if your issue is resolved

2. Creating Port and Protocol Mapping

If you are still getting the same 503 Error Code. Then you have to create port and protocol mapping.

In this case, the 503 Error Code appears when PHP is unable to locate the server port behind Varnish. Thus the communication layer between the WordPress and remote service gets broken.

The only way to resolve this 503 Error Code issue is to create a port and protocol mapping. This will help in translating the proper information over to the PHP engine

3. Incorrect Varnish Cache Configuration

Users have also reported that the 503 Error Code also occurs when the varnish cache configuration is incorrect or wrong. The major thing that is to be set right is mentioned below

503 Error Code

  • Make sure that Varnish and Apache use the same port which is 80
  • Make sure that the IP address used in the Varnish configuration is listening properly

4. Delete Maintenance. flag

If you are using the Magento connect the method is for you. According to the users. The 503 Error CodeΒ occurs because of the file “maintenance. flag” located in theΒ root directory of the Magento website. It put the website into maintenance mode and thus you get the error. To fix this issue simply remove the maintenance. flag.

  • STEP 1. First of all log in to the web host
  • STEP 2. To gain access to your website Host Server, you will need an FTP client
  • STEP 3. Using the FTP client Navigate to the Magneto website root directory
  • STEP 4. Once you have reached look for the file β€œmaintenance. flag” file
  • STEP 5. Once you find it, delete the file
  • STEP 6. Now refresh your website and your error will be fixed

5. WordPress Troubleshooting

Sometimes the 503 Error Code occurs because of small things that are often missed and overlooked by the user.

  • Deactivate plugins: If you have recently installed any plugin or addon, or maybe you have updated any plugging. Make sure to disable it or uninstall it to fix the issue.
  • Switch Theme: Similarly, like plugins, if you have recently installed a new theme or updated the existing theme, then it is suggested to either change the theme or switch to the previous version.


This is the end of the troubleshooting guide on 503 Error Code Backend Fetch Failed. We can conclude that by following the above methods and tips you will surely get rid of this issue. This article covers all the causes of this 503 Error Code issue and its solutions. We hope your issue is fixed. For more guides like this follow us. Thank you!

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People Also Ask (FAQ):

πŸ” Q1: What Mysteries Does the 503 Error Code Conceal?

A: The 503 Error Code is not merely digits on your screen; it’s a ghostly siren warning of server unavailability! Whether due to maintenance or overloading, this code signals that the server cannot handle the request, hurling your users into the void of inaccessibility.

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503 Error Code

A: Employ a custom 503 Error Code page! With a touch of creativity and a dash of informality, your error page can communicate issues effectively, providing reassurance and alternative contact or access points to your besieged digital visitors, turning a potential frustration into a palatable interaction.

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πŸ’Ό Q9: What Steps Should I Take When the 503 Error Code Has Been Vanquished?

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