What is a 503 Service Unavailable Error

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503 Service Unavailable Error

One of the most common errors that occur when browsing the web is the “503 Service Unavailable Error”. This error message happens when the website’s server is facing technical issues and is unable to process your request. It could be due to various reasons, such as server overload, maintenance, or upgrades. This error can be frustrating, but it’s important to understand that it’s not an issue with your device or internet connection. All you can do is wait for the website’s server to resolve the issue or try again later.

This article explains what a 503 error means, why you’re getting an HTTP 503 code, and how to troubleshoot these errors.

What is an HTTP 503 Error

When you open a web page, your browser sends a request to the server hosting the site, which returns the requested data and response code. The server returns the HTTP response status code that tells the client whether the request has been successful or not.

Response codes are categorized into five classes. The codes in the range of 500 to 599 indicate a server error.

The HTTP status code 503 is a generic error response returned when the server cannot handle the request. There are many reasons why a server is not ready to complete the request and return a 503 error. This error code usually appears when the server is overloaded with requests or down for maintenance.

Error 503

If the page you are visiting throws 503 Error, there is nothing much you can do since your browser or Internet connection does not cause the error. Even though the error is on the server side, you can try some of the following options:

  • Reload your browser or try opening the page with another one. The chances that the page will load when you refresh your browser are low, but still, it’s worth giving it a try.
  • Try to clear your browser cache. If the page showing a 503 error is cached, the browser will request a new version after the cache is cleared.
  • Come back later. The web admin may fix the webserver issue in the meantime.
  • Contact the website owners. The last remaining option is to contact the person responsible for maintaining the website.

Troubleshooting 503 Error

Several different reasons could cause the 503 Internal Server Error. The most common are the following:

  • Distributed Denial of Service (DDoS) attack. A DDoS attack is an attempt by a malicious party to flood the bandwidth or resources of your system and overload it. When the system gets overloaded, it is not able to serve the requests. This can result in significant downtime, loss of revenue, and damage to the reputation of the targeted organization.
  • Automated Maintenance. You may not know it, but your server may go through regular service or software maintenance. For example, if you have a WordPress site, it is automatically updated to the latest version whenever there’s a new release. During the update process, WordPress returns a 503 Service Unavailable error.
  • Firewall settings. Often, a misconfigured firewall can cause a 503 error. This usually happens when the application uses a content delivery network (CDN). The server firewall may recognize the requests from the CDN as an attack and block them, resulting in a 503 error.
  • Hacked site. A malicious code that is injected into your website may result in a 503 error.
  • Issues with plugins and themes. If you are running WordPress or a similar CMS, the 503 error can appear after updating or modifying a plugin/theme.
  • Node.js server. If you have a Node.js based site, check if the Node.js server crashed or just not running.

The best way to determine why the 503 error occurred is to check the server log files. The location of the log files depends on your Linux distribution and the webserver. The most common locations for Apache and Nginx are as follows:


If your application is built on Node.js, check the Node.js logs.

Typically, the server log contains detailed information about the error that will help you identify and fix it.


The 503 Internal Server Error is an HTTP status code, meaning that something went wrong with the web server hosting the site you’re visiting. This could be due to various reasons, such as maintenance work, high traffic, or a server overload.

If you have any questions or feedback, feel free to leave a comment.