503 Service Unavailable Error Message: What It Is and How to Fix It

The 503 Service Unavailable error is an HTTP status code that means a website’s server is not available right now. Most of the time, it occurs because the server is too busy or maintenance is being performed on it.

A 503 error message can be customized by the website it appears on or the server software that generates it, so how you might see it vary greatly.

How to Fix the 503 Service Unavailable Error

Since the 503 Service Unavailable error is a server-side error, the problem is usually with the website’s server. Your computer may have an issue causing the 503 error, but it’s not likely.

Regardless, there are a few things you can try:

  1. Retry the URL from the address bar again by selecting Reload or Refresh, the F5 key, or the Ctrl+keyboard shortcut.Even though the 503 Service Unavailable error means there’s an error on another computer, the issue is probably only temporary. Sometimes just trying the page again will work.If the 503 Service Unavailable error message appears while paying for an online purchase, be aware that multiple attempts to check out may end up creating multiple orders and multiple charges. Most payment systems and some credit card companies have protections from this kind of thing, but it’s still something you should know.
  2. Restart your router and modem. Then restart your computer or device, especially if you see the Service Unavailable – DNS Failure error.While the 503 error is still most likely the fault of the website you’re visiting, there may be an issue with the DNS server configurations on your router or computer, which a simple restart of both might correct.If rebooting your equipment didn’t correct the 503 DNS Failure error, there might be temporary issues with the DNS servers themselves. In this case, pick new DNS servers from our Free & Public DNS Servers list and update the servers on your computer or router.
  3. Another option is to contact the website directly for help. There’s a good chance that the site’s administrators already know about the 503 error, but letting them know, or checking the status on the problem, isn’t a bad idea.Most sites have support-based social network accounts, and some even have phone numbers and email addresses.If the website giving the 503 error is a popular one, and you think it might be down completely, check if the website is down by plugging its URL into a service like Freshping’s Is it down tool. An outage on a prominent site will also generate lots of talk on social media.
  4. Come back later. Since the 503 Service Unavailable error is a common error message on trendy websites when a massive increase in traffic by visitors is overwhelming the servers, simply waiting it out is often your best bet. Frankly, this is the most likely “fix” for a 503 error. As more and more visitors leave the website, the chances of a successful page load for you increase.

Fixing 503 Errors on Your Own Site

With so many different web server options out there and even more general reasons why your service might be unavailable, there isn’t a straightforward “thing to go do” if your site is giving your users a 503.

That said, there are certainly some places to start looking for a problem and then hopefully a solution.

Start by taking the message literally—has something crashed? Restart running processes and see if that helps.

Beyond that, look at not-so-obvious places where something might have hiccuped. Where applicable, look at connection limits, bandwidth throttling, overall system resources, fail-safes that might have triggered, etc.

In what’s very likely a “double-edged sword” for your website, it may be that it’s suddenly very, very popular. Getting more traffic than you built your site to handle almost always triggers a 503.

However, the 503 error could also result from a malicious denial of service (DoS) attack. If so, getting into contact with the company hosting your website would be wise to discuss steps that you can take to reduce the likelihood of it happening again or to better prepare for another in the future.

Even an unintentional DoS attack can occur, where a virus on the server is sucking away usable system resources and slowing the server down to the point that it causes a 503 error.

Most Common Ways You Might See the 503 Error

503 Service Unavailable errors can appear in any browser in any operating system, including Windows 10 back through Windows XP, macOS, Linux, etc…even your smartphone or other nontraditional computers. If it has internet access, you could see a 503 in certain situations.

Here are the most common ways you might see the “service unavailable” error:

  • 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

The 503 Service Unavailable error displays inside the browser window, just as web pages do.

Sites that use Microsoft IIS may provide more specific information about the cause of a 503 Service Unavailable error by suffixing a number after the 503, as in HTTP Error 503.2 – Service Unavailable, which means Concurrent request limit exceeded. See More Ways You Might See a 503 Error near the bottom of the page for the whole list.

More Ways You Might See a 503 Error

In Windows applications that inherently access the internet, a 503 error might return with the HTTP_STATUS_SERVICE_UNAVAIL error, and maybe also with a The service is temporarily overloaded message.

Windows Update might also report an HTTP 503 error, but it will display as error code 0x80244022 or with a WU_E_PT_HTTP_STATUS_SERVICE_UNAVAIL message.

Some less common messages include 503 Over Quota and Connection Failed (503), but the troubleshooting above applies all the same.

If the website that reports the 503 error happens to be running Microsoft’s IIS web server software, you might get a more specific error message like one of these:

IIS 503 Errors
Status CodeReason Phrase
503.0Application pool unavailable
503.2Concurrent request limit exceeded
503.3ASP.NET queue full
503.4FastCGI queue full

Errors Like 503 Service Unavailable

The 503 Service Unavailable error is a server-side error. It’s very much related to other server-side errors like the 500 Internal Server Error, the 502 Bad Gateway error, and the 504 Gateway Timeout error, among others.

Several client-side HTTP status codes exist, too, like the standard 404 Not Found error, among others. 


  • When is a 503 Error likely to appear?You can encounter a 503 error pretty much any time you’re visiting a website or using an online service. It’s sometimes possible to anticipate these errors, such as when a small website suddenly receives an unexpected surge in attention it wasn’t built for. However, more often than not it comes down to timing and bad luck whether or not you’ll encounter one.
  • Can a 503 Error appear with any other messages?Yes. It can also appear as Varnish Cache Server: Error 503 Service Unavailable or Error 503: Backend Unhealthy or error when calling aws apis. error details – serializationerror: 503 service unavailable. Regardless of how the message appears, the main terms to look out for are 503 and Error.
  • What should I do if I get a 503 Error when I open Safari on my Mac?This probably means that whatever website you’ve set as Safari’s home page default is experiencing trouble. Aside from waiting a bit and trying again, or restarting Safari or your Mac, you can also change Safari’s home page to a different URL.

Source: 503 Service Unavailable Error Message: What It Is and How to Fix It (lifewire.com)

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