500, 502 and 504 Errors: What They Mean and How to Fix Them

A 500 error means your website's own code or server hit a problem it could not handle, such as a PHP fatal error or running out of memory. A 502 means a server in front of your site (a proxy, load balancer or Cloudflare) got an invalid response from the server behind it, and a 504 means it got no response in time. All three are server-side problems, so visitors cannot fix them; the fix is in your site's code, hosting or server settings.

This guide is for business owners and managers whose site is showing one of these errors, or showed one recently. It explains what each code means, the common causes on WordPress and on servers, what you can safely check yourself, and when to stop and get help.

#What each error means

The codes are defined in the HTTP standard (RFC 9110), and MDN summarises them in plain terms.

The useful difference: with a 502, the server behind the proxy answered but the answer was broken or the connection dropped. With a 504, it never answered within the time allowed. MDN also notes that a 504 can come from the visitor's own network (VPN, firewall, DNS), so if only one person sees it, check from another connection first.

#Common causes on WordPress

On WordPress sites, most 500 errors trace back to one recent change.

• A PHP fatal error after an update. A plugin or theme update that does not work with your PHP version or another plugin. Since WordPress 5.2, this often shows as "There has been a critical error on this website" instead of a bare 500, and WordPress tries to email the site's admin address a recovery link. That email goes to the admin address stored in the database, which may be an old developer's.
• Memory exhausted. WordPress tries to give PHP 40 MB by default on a single site (64 MB on multisite), and many hosts allow more. Heavy page builders, large imports or WooCommerce reports can exceed the limit. The log shows "Allowed memory size exhausted".
• A broken .htaccess file on Apache servers, often after a security or cache plugin edited it.
• A PHP version change by the host, where old code stops working on the new version.
• Wrong file permissions after a migration or manual upload.

If the error appeared straight after updating something, our guide to what to do when a WordPress update breaks your site walks through the rollback.

#Common causes on servers: PHP-FPM, timeouts and upstreams

On a VPS or cloud server, the website usually runs as a chain: Nginx or Apache receives the request and hands PHP work to PHP-FPM, a pool of PHP worker processes. The front server is the "gateway" and PHP-FPM, Node.js or another app is the "upstream".

Each link can fail in its own way:

Raising timeouts and memory limits treats the symptom. If a page needs more than a minute to load, the real fix is usually a slow database query, a slow external service or a job that should run in the background.

#Cloudflare's 52x errors

If your site uses Cloudflare, you may see Cloudflare's own error page with a 52x code. These mean Cloudflare is working, but the connection between Cloudflare and your server failed.

For 524 errors on long tasks like large exports, Cloudflare suggests moving those requests to a subdomain that is not proxied, or reworking them to run in the background. Our guide to setting up Cloudflare for a business website covers SSL modes, which cause most 525 and 526 errors.

#Safe first steps for a site owner

These steps are safe for a non-developer and do not risk making things worse. Do them in order.

1. Note the details. The exact error text, the time (with time zone), which pages show it and whether it happens for everyone. Cloudflare asks for the same details when you contact your host.
2. Check if it is just you. Try a phone on mobile data. If it works there, the problem may be your network.
3. Check your host's status page for an outage in your data centre.
4. Undo the last change. If you updated a plugin, theme or PHP version just before, roll it back, or restore the backup taken before the change.
5. Read the error log. Your host's control panel usually has an error log. The line at the time of the error usually names the file and plugin involved.
6. Disable the plugin it names, or if you cannot log in, rename that plugin's folder in the file manager. Do not delete plugin files.
7. Ask your host to check resource limits, PHP workers and server logs, giving them the details from step 1.

Do not turn on WordPress debug display on a live site; WordPress's own handbook advises against using debug tools on production. If you need the log, write errors to a file instead of showing them on the page.

#When to get help

Get help straight away when the error affects your checkout, payments or logins, when it keeps coming back at busy times, when the error log points to the server rather than a plugin, when you run your own VPS, or when the site may have been hacked (unknown files in the log, strange redirects). Every hour of a 500 on a store is lost orders.

Our emergency WordPress fixes service handles critical errors, white screens and broken updates, usually starting with the logs and a safe rollback. For 502 and 504 errors on your own server, VPS and cloud server management covers PHP-FPM, Nginx, resource limits and Cloudflare. To catch the next one early, see our guides to website monitoring tools and a backup and disaster recovery plan.