White page in the Joomla frontend and backend - troubleshooting

You can see that you see nothing! :-)
A blank white page in the Joomla front end or back end is a common problem that at first leaves many Joomla users puzzled.
The problem: PHP execution stops because of an error.
Most live Joomla installations respond with a completely empty white page.
The first step toward troubleshooting is to make the error visible.

That should make it clear where the problem is occurring.

Bringing the white page to life - enable error_reporting and debug mode

If the white page appears only in the Joomla frontend, you can simply set "Error Reporting" to "maximum" in the System Configuration in the Administrator area. This setting is found in the Server tab. Enabling debug mode (System tab) can also help.

Administrator page is not displayed

If the backend is also down and no error is shown, the direct route is to edit the configuration.php.
Because configuration.php is usually write-protected (CHMOD 444), the file must first be given write permissions.
In FileZilla: right-click - file permissions -> 644

The value for error_reporting is now changed in the corresponding line from 'none', 'default' or '0' to 'maximum'. To debug the system, a 1 is entered in the configuration variable.

public $error_reporting = 'maximum';
public $debug = '1';

If no error message is still displayed, this is probably because error display has been disabled in the PHP configuration. Depending on which web host the site is with, the PHP configuration can be adjusted accordingly in the customer area. Alternatively, a php.ini placed in the root directory with the following content may work.

display_errors = on

If in doubt, information about error_reporting can usually also be found in any well-organized FAQ/help section of the web hosting provider.

Another suitable video on the topic from joomlainfo.ch:

Load YouTube video

Typical causes of blank Joomla pages

1. Failed updates
2. Incorrect / PHP version set too high (possibly automatically raised by the host)
3. Insufficient memory_limit (often caused by visitor counters or gallery extensions when compressing photos that are far too large)
4. Incomplete / only partially uninstalled extension packages

White page after Joomla update

Disable incompatible extensions

After a Joomla update, problems often occur with the extensions in use, which may not be compatible with the new version. Depending on when the incompatibility interferes during the update process, it can also happen that the update fails completely. It is therefore advisable, especially with major version jumps (2.5 to 3), to disable all third-party extensions before the update. A practical approach is to sort by ID in descending order under Extensions -> Manage. Then display 30-100 entries per page, check all entries with ID > 10000 (= 3rd party) and disable them.

If the site is already white due to an incompatibility and displaying an error message, the extension causing the problem can be disabled directly in the database via phpMyAdmin.
-> In the #__extensions table, change the value for 'enabled' from 1 to 0.

Afterwards, the problematic extension can be updated in the backend and re-enabled.

Tip #1 for troubleshooting

Google the error message!
The best results with suitable solutions are obtained when the last part of the displayed error message (/path/filename + line) or key parts of the message are put in quotation marks in the Google search.

Examples:

"/plugins/system/logout/logout.php on line 48"
"JHtmlBehavior::mootools not found."
"/libraries/cms/application/site.php on line 669"
"undefined method JAdminCssMenu::addChild()"
"/modules/mod_sppagebuilder_admin_menu/tmpl/default_enabled.php on line 16"

Joomla is widely used and there is a good chance that someone else has already had the same problem.

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