Troubleshooting Jetpack Boost caching issues

If you receive an error indicating that the cache isn’t working as expected, it’s essential to identify the specific problem based on the error message. Below, you’ll find detailed guidance to troubleshoot and resolve these common caching issues, ensuring your site’s caching is optimized and functional.

File access problems

Issue: Jetpack Boost’s page cache needs to update specific directories and files within your wp-content directory to function correctly. These critical locations include:

• wp-content: The primary content directory of your WordPress installation, where Jetpack Boost tries to create a boost-cache subdirectory.
• wp-content/boost-cache/: Contains Jetpack Boost’s page cache configuration and cached content, which must be writable.
• wp-content/boost-cache/config.php: Holds the page cache configuration and needs to be writable.
• wp-content/advanced-cache.php: Facilitates serving cached content before WordPress fully loads and must be writable.

Solution: Check and adjust the permissions of these files and directories to ensure they are writable by WordPress. Use FTP/SFTP to set file permissions to CHMOD 644 or 666 and directory permissions to 755 or 775. This enables Jetpack Boost to cache your site’s content effectively.

Incompatible permalinks settings

Issue: Jetpack Boost’s caching does not support the “Plain Permalinks” setting, due to its reliance on unique URLs for efficient content caching and retrieval.

Solution: Change to pretty permalinks by going to Settings → Permalinks in your WP Admin. Select any option other than “Plain” and save your changes.

Advanced cache incompatibility

Issue: Conflicts with an existing caching system, installed by another plugin or your hosting provider, can impede Jetpack Boost’s caching.

Solution:

• Deactivate any conflicting caching plugins via the Plugins section in WP Admin.
• For hosting-related caching conflicts, consult your provider to resolve the issue, potentially by disabling their caching solution.
• If your hosting provider comes back to you and the issue is not resolved, check if there’s a file called advanced-cache.php in your wp-content directory. If there is one, delete it.

If you’re seeing layout issues rather than caching errors, it may be caused by a plugin conflict affecting CSS. See Potential Conflicts with Other Performance Plugins for more details.

Advanced cache for WP Super Cache

Issue: If WP Super Cache is active, it can conflict with Jetpack Boost’s caching mechanism.

Solution: Deactivate the WP Super Cache via the Plugins section in your WP Admin to eliminate the conflict and enable effective caching with Jetpack Boost.

Unable to write to advanced-cache.php

Issue: Jetpack Boost requires a writable advanced-cache.php file to efficiently serve cached content.

Solution: Adjust the advanced-cache.php permissions within the wp-content directory to CHMOD 644 or 666, ensuring Jetpack Boost can modify the file as needed.

WP_CACHE defined but not true

Issue: The WP_CACHE constant in wp-config.php must be true for Jetpack Boost to use WordPress caching capabilities. A false setting prevents activation.

Solution: Locate and modify the WP_CACHE definition in wp-config.php. Change it to true if set to false or add define( 'WP_CACHE', true ); above the "That's all, stop editing! Happy publishing." line if not defined.

WP-Config not writable

Issue: Write protection on wp-config.php can prevent Jetpack Boost from adding the necessary PHP line for caching activation.

Solution: Manually adjust wp-config.php permissions to make it writable, or add define( 'WP_CACHE', true ); manually if permissions are restricted. Ensure this line is placed above the "That's all, stop editing! Happy publishing." comment.

By identifying the specific issue based on the error message and following these solutions, you can address common problems with Jetpack Boost’s caching feature, improving your site’s performance and user experience.

Manually Deleting the Boost Cache Directory

Issue: In some cases, using the “Clear Cache” button in Jetpack Boost may not fully remove cached files from the /wp-content/boost-cache/ directory. This can lead to the accumulation of unnecessary files, contributing to high file server usage.

Solution: It is safe to manually delete the /wp-content/boost-cache/ directory if the “Clear Cache” button does not remove the files as expected. After manually deleting the folder, Jetpack Boost will regenerate the necessary cache files when it is enabled again. You can do this by accessing your site’s file manager through FTP/SFTP or your hosting provider’s control panel.

Resetting Jetpack Boost Cache After Conflicts

Issue: In some cases, Jetpack Boost’s caching feature may stop working correctly after enabling and disabling different caching plugins or making repeated changes to your site’s caching setup. If the Boost cache doesn’t activate even though it appears everything is in place, a full reset can often resolve the issue.

Solution: Follow these steps to reset the Boost cache configuration:

1. Uninstall other caching plugins, even if they’re inactive. Do this from the Plugins page in WP Admin (don’t delete them manually via FTP). This ensures the plugins can run their cleanup routines.
2. In the Boost settings, deactivate the Boost cache module (if it’s currently on).
3. Delete the /wp-content/boost-cache/ folder using FTP, SFTP, or your host’s file manager.
4. Delete the wp-content/advanced-cache.php file, if it exists.
5. Open your wp-config.php file and look for a line like define( 'WP_CACHE', true ); — remove it or comment it out if present.

After completing these steps:

• Reactivate the Boost cache module from the Boost settings.
• Boost will recreate the necessary files and regenerate its cache configuration.

This reset is especially helpful if caching broke after switching between multiple plugins or hosts. If you’re unsure about any of the steps, your hosting provider may be able to help.

Get help

Need more help? Feel free to contact us! For free Jetpack Boost users, you can post a support request on the Jetpack Boost Plugin Support page. If you upgraded, you can contact support for more personalized assistance.