Quick answer
You find the culprit for a plugin conflict fastest by deactivating all plugins, then activating them one by one and checking after each whether the problem returns. If the issue occurs only on one page or in one form, repeat the same procedure with the active theme. First of all, make a backup of the site and work on a copy or outside working hours.
How to recognize the problem
- The site or part of the site stops working after a plugin or WordPress update
- Page elements do not display, layout breaks, or a white screen appears
- The error occurs only when logged in as administrator, visitors do not see it
- Contact form, shop, or gallery stops working without an obvious reason
- The same message related to one plugin folder repeats in the error log
Most common causes
Two plugins do the same thing
Two caching, image optimization, or backup plugins often block each other because they handle the same requests. The conflict then appears only when both are active.
Incompatible version with WordPress or PHP
A plugin that has not been updated for the current WordPress or PHP version can cause errors that are visible only on certain pages. Checking compatibility on the plugin page in the repository reveals such cases.
Conflict with the active theme
Some plugins rely on functions that the theme modifies or removes, so the issue appears only with that theme. That is why the theme is checked separately from plugins.
Corrupted file or incomplete update
An interrupted update or an incompletely transferred plugin file can leave missing files. The plugin is then active but cannot load correctly.
Leftover from a deactivated plugin
A database table or option left behind by an old plugin can affect a new plugin with the same purpose. The problem then does not disappear even after deactivation.
Step-by-step fix
- 1
Make a backup and record the state
Before any changes, make a full backup of the site, files, and database, preferably with a backup tool or through the hosting panel. Write down which plugins you have and their versions so you can restore the exact state. If the site is in production, work outside working hours or on a copy of the site on a test domain.
- 2
Enable error logging in WordPress
Temporarily in the
wp-config.phpfile setdefine('WP_DEBUG', true);,define('WP_DEBUG_LOG', true);, anddefine('WP_DEBUG_DISPLAY', false);, then check thewp-content/debug.logfile. Messages in the log often name the plugin folder causing the problem, which immediately narrows down the suspects. When done, setWP_DEBUGandWP_DEBUG_LOGback tofalse, andWP_DEBUG_DISPLAYto its previous value. - 3
Deactivate all plugins at once
Go to
Plugins > Installed Plugins, select all plugins, and chooseDeactivatefrom the drop-down list, then apply. If the problem does not occur after that, it is confirmed that a plugin is causing it. If it still occurs, the cause is most likely the theme or the database, so move on to the theme step. - 4
Activate plugins one by one
Activate the first plugin, then check the page where the issue occurred. Then activate the next one and check again. Repeat the procedure until the problem returns; the plugin you activated last is the culprit or one of the two plugins in conflict.
- 5
Check the combination of two plugins
If the problem returns only when two plugins are active, deactivate one of them and leave the other. Then swap roles: deactivate the second and activate the first. This confirms that the conflict is between them, not that one plugin alone causes the error.
- 6
Check the theme in the same way
If the issue occurs even with all plugins deactivated, switch to the default theme. Go to
Appearance > Themes, activate the theme that comes with WordPress, and check the site. If the problem disappears, the previous theme or its settings are to blame, not a plugin. - 7
Revert the plugin to an older version
Once you know the culprit, check if an older version of the plugin is available. On the plugin page in the repository, find the section with previous versions and download the
.zip, then upload it viaPlugins > Add New > Upload Plugin. Revert to an older version only if it is security-safe; if that does not help either, look for an alternative plugin with the same purpose. - 8
Reactivate all other plugins and clear the cache
Reactivate all plugins except the culprit, then clear the site and browser cache. If you use a caching plugin, clear the cache from its menu, and clear the browser cache through the browser settings. Check the site in a private browser window, and if necessary disable extensions to rule out their influence.
If nothing helps: safe deactivation via the file system
When you cannot log in to the admin due to an error, you can deactivate plugins via the hosting panel or an FTP client. Open the wp-content/plugins folder and rename the folder of the problematic plugin, for example from plugin-name to plugin-name-off. WordPress then does not see the plugin and automatically deactivates it. You can do the same with the theme folder in wp-content/themes, but only if you have previously activated another theme; otherwise the site may be left without a design. After each change, refresh the site page and check if the error returns. When done, restore the original folder names. If the error occurs even with plugins deactivated and the default theme, the cause is probably in the database or core files, so the next step is to restore the site from a backup.
How to prevent it
- Update plugins regularly, but first on a site copy and with a backup
- Keep the minimum possible number of plugins and remove those you do not use
- Before any major update, record plugin and theme versions
- Use plugins with active maintenance and verified compatibility
When to call a professional
If the error repeats even after deactivating all plugins and changing the theme, or if you cannot even open the site, it is better to call IT support than to further modify files and the database without a backup.
Website development · Fast, SEO-ready, multilingual websitesFAQ
How do I know which plugin is causing the error if I cannot log in?
Via the hosting panel or FTP, open the `wp-content/plugins` folder and rename the plugin folders, then check the site after each change. If necessary, temporarily rename the entire `wp-content/plugins` folder to `wp-content/plugins-off`, then restore it after checking. Do not change `wp-config.php` if you are not sure what exactly you are changing.
Is it safe to deactivate all plugins on a production site?
Brief deactivation is a common procedure, but visitors during that period may see the site without certain features, for example without the shop or form. Therefore, work outside working hours, on a site copy, or in maintenance mode.
What if the problem occurs only when I am logged in?
This indicates cache or a plugin that changes the display for logged-in users. Clear the site and browser cache, then check the site in a private window. If the problem does not occur there, deactivate plugins using the same procedure.