Back to Community
Home / Community / Plugin → Smush image optimization – optimize images | compress & lazy load images | convert webp & avif | image cdn

Troubleshooting Common Smush Plugin Issues: From Database Errors to Loopback Requests

30 threads Sep 11, 2025 Plugin → Smush image optimization – optimize images | compress & lazy load images | convert webp & avif | image cdn

Content

Users of the 'Smush Image Optimization – Optimize Images | Compress & Lazy Load Images | Convert WebP & AVIF | Image CDN' plugin occasionally encounter issues that can prevent it from working correctly. Based on community reports, here are some of the most common problems and their potential solutions.

1. Database Table Missing Primary Key

The Problem: Some users on cloud hosting providers like Digital Ocean report an error related to the wp_smush_dir_images table lacking a primary key. This is a strict requirement for MySQL 8 and database replication.

The Solution: This is a known issue that has been reported to the Smush development team. While they have stated it should not have negative side effects, they are investigating its impact on modern MySQL setups and cloud providers. Users experiencing this issue should monitor official channels for a future plugin update that may address the database structure.

2. Loopback Request Errors

The Problem: The plugin may display a message stating, "Your site seems to have an issue with loopback requests," even if the WordPress Site Health tool reports no problems. This can prevent Smush from finding images.

The Solution:

  • Check Security Plugins: Some security plugins, like All-In-One Security (AIOS), can block the necessary loopback connections. Review your security plugin's settings, particularly any URL or firewall rules that might be interfering.
  • Hosting Configuration: Contact your hosting provider to confirm that loopback connections to your own domain are enabled and not being blocked by their firewall.
  • Manual Rules for Hybrid Setups: If you are on a hybrid NGINX/Apache server (e.g., Cloudways, Nexcess), you may need to manually add NGINX rules to allow WebP serving, as the standard .htaccess rules may not work.

3. "Error posting to API: 404 Not Found"

The Problem: Users may suddenly be unable to smush images and see this API error message.

The Solution: This error typically indicates a temporary problem on the Smush API servers. In most cases, the issue is resolved on their end within a short period. If the error persists, a good first step is to check the status of the Smush service on independent forums or status pages.

4. Images Not Found or Not Smushing on Upload

The Problem: Smush may fail with a "Could not find [image path]" error or may not automatically optimize images upon upload.

Potential Causes and Solutions:

  • Custom Uploaders: Themes or plugins with custom file uploaders (e.g., certain forum plugins, classified ads themes) may not trigger Smush's automatic optimization. For images stored outside the standard media library, use the Directory Smush feature to manually optimize them.
  • Image Offloading: If you use a plugin like Jetpack or WP Offload Media that moves images to a CDN or cloud storage, the physical files may be removed from your server. Smush can only optimize images that are physically present on your server at the time of upload.
  • Conflicting Optimization Plugins: Ensure you do not have another image optimization or lazy load plugin active, as they can conflict with Smush.

5. Performance and Timeout Issues

The Problem: Smush can sometimes cause slow page loads, timeouts during upload, or slow admin pages, especially on sites with a large number of images.

The Solution:

  • Disable Async Processing: Add the following line to your wp-config.php file to disable asynchronous processing, which can resolve some timeout issues: define( 'WP_SMUSH_ASYNC', false );
  • Check for Conflicting Functions: If using a front-end upload form (e.g., with ACF), you may need to try disabling auto-compression for that specific action using custom code.
  • Large Media Libraries: A known issue with slow database queries on the Smush admin page for large libraries has been addressed in newer versions. Ensure your plugin is updated to the latest version.

General Troubleshooting Steps

For any persistent issue, always try this basic checklist:

  1. Update: Ensure WordPress, your theme, and all plugins are updated to their latest versions.
  2. Conflict Test: Temporarily switch to a default WordPress theme (like Twenty Twenty-Four) and disable all other plugins except Smush. If the problem resolves, reactivate them one-by-one to identify the conflict.
  3. Reinstall: Completely uninstall and then reinstall the Smush plugin.

By methodically working through these common problems, you can often resolve issues and get the Smush plugin working smoothly on your site.

Related Support Threads Support