What Does HTTP Error 503 (Service Unavailable) Mean & How To Fix It?

Imagine someone searches for a topic and finds your website on page one of Google. When they click through to your website, though, their eyes land on a bland webpage that says "Service Unavailable".

What do you think they'll do when they find your website on Google again? Odds are, they'll skip over it and click on the next link. If visitors are looking for answers and you're promising them those answers, but you can't deliver because something's wrong with your website, they'll lose trust in your brand.

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Unfortunately, if your website experiences a 503 Service Unavailable Error, there's no silver bullet solution. You have to investigate what's actually causing the issue, because even though these types of errors indicate what happened to your website, they don't tell you why it happened.

To help you fix your 503 Service Unavailable Error and avoid losing potential customers, check out our guide on what exactly the issue is and its most common solutions.

What is a 503 error?

A 503 Service Unavailable Error is an HTTP response status code that indicates your web server operates properly, but it can't handle a request at the moment. Since it's just a generic error message, it's difficult to pinpoint the issue's exact cause.

When your website is experiencing a 503 Service Unavailable Error, your site's visitors will land on an error page. Fortunately, Airbrake recommends five common solutions for troubleshooting most 503 Service Unavailable Errors.

How to Fix an HTTP Error 503

1. Reboot your server.
2. Check to see if your web server is going through maintenance.
3. Fix faulty firewall configurations.
4. Sift through your server-side logs.
5. Comb through your website's code to find bugs.

1. Restart your server.

Sometimes, there will be congestion in the server chain that hosts your website. One of the most effective ways to open up and refresh it is to simply restart your web server. If your website is hosted on multiple servers, make sure you restart all of them to get it running again.

2. Check to see if your web server is going through maintenance.

Most web servers shut down when they're going through maintenance. If you can access your server's administration settings, check the configuration options to see when automatic maintenance sessions are scheduled. If you'd rather have complete control over your server's maintenance, you can disable these automatic updates in the configuration options, too.

3. Fix faulty firewall configurations.

Your firewall is your website's gatekeeper, protecting your site from malicious visitors or distributed denial-of-service (DDoS) attacks. Sometimes, a faulty firewall configuration will cause your firewall to deem requests from a content delivery network as an attack on your server and reject them, resulting in a 503 Service Unavailable Error. Check your firewall configuration to pinpoint and fix the issue.

4. Sift through your server-side logs.

There are two types of server-side logs -- applications logs and server logs. Application logs recount your website's entire history, letting you see the web pages requested by visitors and the servers it connected to. Server logs provide information about the hardware running your server, revealing details about its health and status. Sift through both types of server-side logs to uncover any alarming information about your server or website.

5. Comb through your website's code to find bugs.

If there's a mistake in your website's code, your web server might not be able to correctly answer requests from a content delivery network. Comb through your code to find bugs or copy your code into a development machine. It'll perform a thorough debug process that will simulate the exact situation your 503 Service Unavailable Error occurred in and allow you to find the exact moment things went wrong.

Any time there's an error on your site, it's important to fix it as soon as you can. If customers get errors, they probably won't come back to your page.

Editor's note: This post was originally published in January 2019 and has been updated for comprehensiveness.