My site shows error 500 after an update

Why it happens

Error 500 means PHP stopped with an error. After an update, the usual cause is an extension or template that isn't compatible with the new Joomla or PHP version. A newly installed plugin can even block the administrator login.

Joomla hides the real message on a live site for security, so the first step is always to see it.

Find the cause

1. If the administrator works: System → Global Configuration, set Debug System to Yes (System tab) and Error Reporting to Maximum (Server tab).
2. If it doesn't: set configuration.php to 644, change $debug to true and $error_reporting to 'maximum', and save.
3. Reload the page and read the error. The path in it (for example /plugins/system/xyz/) names the extension.

Fix it

1. Disable that extension in System → Manage → Extensions. Without administrator access, set enabled to 0 for it in the #__extensions table in phpMyAdmin. Don't disable core extensions.
2. Update or replace the extension.
3. Run System → Maintenance → Database → Update Structure if it lists problems.
4. Set Debug System back to No and Error Reporting to System Default.

Good to know

• The free Forum Post Assistant (FPA) creates a report you can post on the Joomla forum when you are stuck. Remove it afterwards.
• A PHP version change by your host causes the same error: check System Information.