What is HTTP 503 (Service Unavailable) Error? How to fix it?

What do HTTP status codes mean?

HTTP is an abbreviation of HyperText Transfer Protocol, which is a communication protocol that determines the rules between the client and the servers to view webpages. For debugging purposes when a problem occurs, the HTTP generates codes to indicate the current status of the website.

There are five types of codes, and all of them are grouped with the first number of the code. For example, the codes that begin with “2”, like 201, indicate the success of the processes. You can see the HTTP status types below:

• 1XX: Informational response
• 2XX: Success
• 3XX: Redirection
• 4XX: Client errors
• 5XX: Server errors

You might as well want to check our article about all of the official HTTP status codes. There are unofficial status codes as well, which were created by the companies to deliver platform-specific information. But HTTP 503 error is one of the official ones and as you can see, it falls under the Server Errors category.

What is HTTP 503 error and what can cause it?

HTTP 503 error means that the server is currently not available. There might be many reasons behind this issue. The electricity or the internet connection to the server might be cut, or the server itself might be shut down.

The problem could be a temporary one as the hosting company that hosts the website’s server can be having an outage. Additionally, it might also be an ongoing DDoS attack on the server/website. But the owner might also have completely shut the website as well. Overall, you can think of the HTTP 503 code as the server either can’t send any signals to the internet indicating it exists, or it is not working for any reason.

The HTTP 503 error message can also appear as the ones that are listed below:

• 503 Service Unavailable
• 503 Service Temporarily Unavailable
• HTTP/1.1 Service Unavailable
• HTTP Server Error 503
• Service Unavailable – DNS Failure
• 503 Error
• HTTP 503
• HTTP Error 503
• Error 503 Service Unavailable
• Error 503 Backend fetch failed
• HTTP Error 503 The service is unavailable
• Status code HTTP Error 503
• 503 Service Unavailable Error
• Error 503 Maximum threads for service reached
• HTTP Error 503

How to fix the HTTP 503 error as a visitor

As a visitor of a website that generates an HTTP 503 error, you don’t have many options to fix the problem. Since the problem is happening on the server side, the administrators of the website or the hosting company need to take care of it. As a visitor, you can refresh the page to see if the problem was fixed by the admins or not. Keep in mind the website you are trying to reach could be completely shut down as well.

How to fix the HTTP 503 error as an administrator

As we mentioned before, HTTP 503 error means either your server is having connection issues when reaching the internet or it is completely down. Administrators can check for the possible causes of the problem, which are listed below:

• The server might be going through maintenance; admins can simply wait for it to end.
• Your firewall configuration might be wrong; admins should check and verify the firewall settings.
• The electricity or the internet for your server might be down; admins should immediately contact the hosting company.
• There might be an ongoing DDoS attack; admins should apply the DDoS attack-preventing procedures or immediately contact the hosting company.
• The resources of your hosting plan might be insufficient even while there is no ongoing DDoS attack; admins should verify if it is the case on their management dashboard and take the necessary actions like going for a higher hosting plan.
• There might be a DNS-related problem; admins should flush DNS by taking the proper steps depending on their servers’ operating systems.

Additionally, the admins should check the logs of their server; there is a good chance to find some valuable information regarding the cause of the HTTP 503 error. You can see the default paths for the error logs of popular web servers and services below:

Since it miraculously fixes most of the issues unexpectedly, the admins can consider rebooting the server as well.