What is HTTP error 503 and how do you fix it?

When you see this error on the internet there is an easy fix

HTTP error 503 service unavailable

One of the most frustrating error messages as both a developer and as a website user is the "503" error message when trying to access a website.

The reason it's so frustrating? Like many other "50-" errors, it's not particularly detailed. Sure, you may know its a server error, but what exactly is causing the problem?

We explain what a 503 error is, how it can present itself and how it can be fixed if it's causing you headaches and stunting your productivity.

What does HTTP error mean?

Although in some cases, a 503 error usually refers to an internet connection problem, with the network unobtainable, it's most commonly a problem on the server-side, meaning client requests can't be fulfilled as expected.

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You may see a suggested action, such as "retry after" in the header message, along with a suggested time frame for retrying to access the site, or it may not even be that helpful.

When does HTTP error 503 happen?

HTTP 503 errors can occur for a multitude of reasons, and it can be difficult to determine the root cause in many of these cases.

One common issue, however, in almost every 503 error relates with the server, and more specifically its inability to send requested resources as calls are made to it. This, too, can be explained by many different factors, such as the hosting company experiencing difficulties, or that the server might be undergoing maintenance. It can happen to everyone but tends to strike some hosting companies more than others. Experiencing this issue repeatedly may be a sign that it's time to explore alternative hosting options.

Seeing the 503 error may also suggest a server doesn't have the capacity needed to serve end-users with resources being demanded. This would normally be due to a spike in traffic or, in extreme instances, a full-blown DDoS attack. Another reason for experiencing a 503 error may be due to misconfigured web apps. WordPress, for instance, could present a plugin conflict.

Meanwhile, a sporadic 503 server error on a particular site could point to a problem with its domain name system (DNS); either an incorrect server configuration on the client's side or a problem with the actual DNS server.

There are clearly many reasons why one may encounter a 503 error while running a site, or trying to access one, but the main priority at this stage should be how to get that site back on its feet.

How to fix HTTP 503 errors

The easiest solution is to refresh the page and see if that can bring it back.

You can also attempt to restart your computer or router. If the error message shows "Service Unavailable -- DNS Failure", there may be a fault with the DNS configuration of the computer or the router. A router problem can be fixed by restarting it. In the case of a problem with a selected DNS server, it may be fixed by choosing another DNS server to use.

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If the HTTP error 503 happens a lot to users of a website, then the administrator needs to troubleshoot the issue and find the appropriate fix.

If there are updates needed for a website, schedule these at a quieter time so that users don't see this message regularly.

If spikes in traffic are causing the error, then it may well be time to increase web server resources to cope with the increase in visitors.

If the error is caused by a denial of service (DoS) attack, it is a good time to contact a hosting provider to see what mitigations can be put in place to avoid this happening again. You may want to look at increasing security or applying patches that hackers may use to attack your website and take it offline.

Lastly, if the error is due to a programming error, further investigation will be required to pinpoint the issue and take steps to correct it.

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