Status Code 503: What Does Service Unavailable Mean?

Similar to how the London Underground aims for a ‘good service on all lines’, every website owner wants the same for their website too. But, if your visitors are being confronted with a 503 service unavailable status code, then trouble is brewing. In this post we will go over why you might be seeing a 503 service unavailable status code and what to do about it. 

503 Service Unavailable

In short, the 503 Service Unavailable error indicates a controlled or temporary downtime status such as server over-usage, an unpaid bill, maintenance or similar. It is usually accompanied with informative text and a code that indicates the planned outage time, a “retry-after” value in seconds. The web server may return text values such as:

  • HTTP Error 503 Service is unavailable
  • HTTP Server Error 503
  • Error 503 Service Unavailable

Overview of 5xx Status Codes

The 5xx range of web server status codes denote that there has been a server error. This means the client (Chrome, Firefox etc) cannot load the content for the user because there is a problem within the server. 

  • 500 internal server error
  • 501 not implemented
  • 502 bad gateway
  • 503 service unavailable
  • 504 gateway timeout
  • 505 HTTP version not supported
  • 509 bandwidth limit exceeded
  • 599 network error timeout

Unlike a 4xx status code, the issue is not the browser you are using. So even if you try and load the page up on another device or browser, you will still get the same issue, because the problem originates at the place where the website is stored – the server. 

503 Service Unavailable: An Overview

Have you ever dialled a number, only to hear a jingle telling you the number is no longer in service? The reason is usually that the person has changed their number, or has even been cut off by their provider so cannot receive any calls. 

The same can also happen with websites via a 503 service unavailable status code. Essentially, the server is communicating to the browser that this website cannot be accessed. 

503 service errors can be extremely frustrating for users. After all, the page cannot be loaded, and there is no information why this is the case, nor a redirect to take them elsewhere. All they know is that the link they really wanted to access will not load. So, they’ll immediately exit the page and look elsewhere, which is bad for the website’s ranking.

In terms of SEO, a longer term outage will affect search rankings. It’s usually a matter of days rather than hours but if it does continue for days, Google may start to lower the rankings for the site. This may appear in Google Search Console statistics. As GSC generally includes it’s own delays, it’s not a good way of monitoring site health.

The good news is that 503 service errors are usually only temporary. Once the server provider has seen that their customers are getting 503 service errors, they will usually be quick to resolve things. 

500 Internal Server Error Vs 503 Service Unavailable

In many ways, 503 service unavailable is similar to 500 internal server error. Either way, there is a problem with the server meaning the content cannot be loaded. 

However, the main difference is that with a 500 internal server error this status code is unexpected. There is a problem with the server and you are not sure what has caused it. You’ve done everything correctly, but for some reason, your website isn’t loading. It’s a pain but is usually resolved quickly by the server provider. 

With a 503 service unavailable, there will be an expected reason as to why your website or page is generating this error. For example, you have exceeded your user numbers and the server is overloaded. Or you haven’t paid your bill so your server provided has halted your plan, meaning your website now won’t load correctly. There may be cases that apply only to you, or a set of specific users but in general, the same message will be seen by everyone accessing the site.

After seeing a 503 error

The normal response is to try to reload the page. If the error was transient, perhaps due to server overload, you might be OK on the second try.

If the error is occurring on your own rented web server, you’ll need to check your server status via your web server console or control panel. Check your emails for messages from your service provider.

There could be technical problems such as load, disk problems, PHP problems, MySQL problems or problems triggered by server management systems such as local DNS issues. Maybe WordPress is in maintenance mode due to a software update.

If you don’t control the web server, the only things you can do are to wait, or, if possible, contact the web server owner to communicate with human-level codes!

And remember, if a server is returning an error, it means it is actually up and running at the IP and web-server layers so the client-side, the browser, is generally OK.


If your website cannot be loaded from the server, a 503 service unavailable message will be displayed. The cause of this error can usually be traced to a problem you will already be aware of, such as exceeding the number of visitors on your site that your web hosting plan allows for. Promptly dealing with 5xx errors of any kind will ensure your SEO rankings are not negatively impacted as a result. 

Steve Paine