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Troubleshooting WP Super Cache Preload Issues: A Comprehensive Guide

47 threads Sep 9, 2025 Plugin → Wp super cache

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WP Super Cache's preload feature is a powerful tool for generating cached files in advance, ensuring visitors experience fast page loads. However, users often encounter issues where preload doesn't work as expected. Based on community reports and troubleshooting threads, this guide covers the most common preload problems and their solutions.

Common Preload Issues and Their Solutions

1. Preload Gets Stuck or Won't Cancel

Many users report that the preload process becomes stuck, often showing an active status indefinitely. The cancel button may also fail to work, displaying a message that cancellation is in progress without ever completing.

Why this happens: This is often related to a stuck process or a conflict with the WordPress cron system.

Potential solutions:

  • Manual file deletion: Look for a file named stop_preload.txt in your cache directory. If it exists, delete it. This file is created when you press cancel, and its presence can sometimes prevent a new preload from starting or an old one from properly terminating.
  • Check your cron setup: If you are using a system cron job to trigger wp-cron.php (common when DISABLE_WP_CRON is set to true), ensure it is configured correctly. Conflicts with other cron management plugins (like "Advanced Cron Scheduler") have been known to cause multiple, overlapping preload tasks that can hang. Try disabling such plugins to test.
  • Debug mode: Enable debugging in WP Super Cache's "Debug" tab. The debug log may provide clues about PHP errors or specific URLs that are causing the process to hang.

2. Preload Doesn't Generate Any Cache Files

You click "Preload Cache Now," see a countdown, but afterward, the cache remains empty. No supercached files are created.

Why this happens: The most common cause is a conflict with another service that intercepts the preload requests, such as Cloudflare. It can also be due to an incorrect site URL configuration, especially after moving from HTTP to HTTPS.

Potential solutions:

  • Cloudflare conflict: You cannot effectively preload a cache if your site uses Cloudflare. The plugin's preload bot will only receive cached responses from Cloudflare's edge network instead of generating new cache files on your server. You must choose to use either Cloudflare's cache or WP Super Cache's preload feature; they are largely incompatible for this specific function.
  • HTTPS configuration: If you recently enabled SSL/HTTPS, ensure your WordPress Address and Site Address are updated to https:// in Settings > General. You may also need to update your .htaccess rules manually to handle HTTPS requests correctly.
  • Check for login cookies: The debug log may show lines like "Login/postpass cookie detected." This indicates the preload process is being treated as a logged-in user and will not cache pages. Ensure you are not logged into your site in the same browser and that no other plugins are setting unexpected cookies for preload requests.

3. Specific Page Types (WooCommerce, Taxonomies) Don't Preload

Preload works for posts and pages but fails to cache product categories, tags, or other custom taxonomy archives.

Why this happens: By default, the preload function may not include all custom taxonomies.

Potential solution:

  • You need to use the wp_cache_preload_taxonomies filter to explicitly include custom taxonomies like product_cat. Adding a code snippet to your theme's functions.php file can resolve this. (Note: Always back up your site before editing theme files).

4. Preload Button is Missing or Interface is Broken

After an update, the "Preload Cache Now" button might be missing from the admin interface, making it impossible to start the process.

Why this happens: This is typically a bug introduced in a specific plugin version.

Potential solution:

  • Check the plugin's support forums for any known issues with your version. A bug reported in version 1.10.0, for example, was fixed by a one-line code change. Waiting for an official patch or carefully applying a recommended code fix can resolve this.

5. Cache Files Are Deleted Too Early By Preload

Preload seems to override your configured cache timeout, deleting files before they are stale.

Why this happens: A confirmed code issue exists where the preload function overrides the global $cache_max_time variable without checking if it was already set to a higher value.

Potential solution:

  • This requires a code patch to the wp-cache.php file. Monitor the official plugin repository for a permanent fix in a future update.

General Preload Troubleshooting Tips

  • Enable Debugging: The single most useful step is to enable the debug log in the plugin's "Debug" tab. This log provides a real-time, detailed account of what the plugin is doing, including errors and which URLs it is attempting to cache.
  • Garbage Collection: Some users have reported that disabling the "Garbage Collection" scheduler can help preload run more reliably. This is worth testing if you are stuck.
  • Manual Cron: If you use a system cron, set it to run less frequently (e.g., every 10-15 minutes instead of every 5) to prevent overlapping processes.

Remember, preload is a complex process that interacts heavily with your server's configuration, WordPress cron, and other plugins. Isolating the cause often involves methodically disabling other plugins and services to identify the conflict.

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