Understanding and Fixing the 'smush_check_for_conflicts' Cron Job Issue

Many users of the 'Smush Image Optimization – Optimize Images | Compress & Lazy Load Images | Convert WebP & AVIF | Image CDN' plugin encounter warnings in their WordPress Site Health tool related to a specific cron job named smush_check_for_conflicts. This article explains what this event is, why these warnings appear, and the most common solutions to resolve them.

What is the 'smush_check_for_conflicts' Cron Job?

This is a background maintenance task the Smush plugin uses. Its sole purpose is to check if any plugins known to conflict with Smush are active on your site. If it finds one, it displays a warning to alert you. It is not related to image optimization, bulk smushing, or the number of images on your site. Its failure or delay will not affect Smush's core image compression or lazy loading functionalities.

Common Error Messages

You might see one of the following messages in Tools > Site Health > Status:

• "The scheduled event, smush_check_for_conflicts, is late to run."
• "The scheduled event, smush_check_for_conflicts, failed to run."

Why Do These Warnings Appear?

There are a few primary reasons for these Site Health notifications:

1. Low Website Traffic: WordPress's built-in cron system relies on visitor traffic to trigger scheduled tasks. On low-traffic or new sites, if no one visits when the task is scheduled to run, it will be marked as "late."
2. WP Cron is Disabled: Sometimes the constant define( 'DISABLE_WP_CRON', true ); is added to the wp-config.php file to switch to a server-level cron, but the server cron may not be set up correctly.
3. Past Plugin Bug (Likely Resolved): Analysis of community threads indicates a bug existed in older versions of the plugin where this event could get stuck in a rescheduling loop. The 'Smush Image Optimization' team has confirmed this was an issue that should have been fixed in previous updates.

How to Troubleshoot and Fix the Issue

1. Verify Your Plugin is Updated

First, ensure you are running the latest version of the Smush plugin. The development team has addressed issues with this cron job in past updates, so updating is the easiest first step.

2. Check Your WP Cron Configuration

Examine your site's wp-config.php file (located in your site's root directory). Look for the following line:

define( 'DISABLE_WP_CRON', true );

If this line is present, it means your site is configured to use a server cron (real cron) instead of the default WordPress cron. You have two options:

• Option A: Set Up a Server Cron Job. If DISABLE_WP_CRON is set to true, you must configure a cron job on your server to regularly call the wp-cron.php file. The exact steps depend on your hosting provider. You can usually find this option in your hosting control panel (e.g., cPanel). A common command to run every 15 minutes is:

  wget -q -O- https://yourdomain.com/wp-cron.php?doing_wp_cron > /dev/null 2>&1

  Contact your hosting support for assistance with this.
• Option B: Re-enable WordPress Cron. If you do not want to manage a server cron, you can remove or comment out the DISABLE_WP_CRON line from your wp-config.php file. This will revert to the default WP cron system that runs on page visits.

3. For Low-Traffic Sites

If your site has very few visitors, the cron event being late is often a false positive and is generally harmless for this specific Smush task. You can safely ignore the warning, as it does not impact site functionality. To make the warning go away, implementing a server cron (as described above) is the most effective solution.

Can I Disable This Cron Job?

While it is technically possible to unschedule the event using code, it is not generally recommended. The task is designed to be lightweight and run infrequently. Manually removing it could prevent you from receiving important conflict warnings in the future. The best course of action is to ensure your site's cron system is configured correctly.

Conclusion

A "late" or "failed" smush_check_for_conflicts event is, in most cases, a symptom of a misconfigured or underutilized WordPress cron system rather than a critical problem with the Smush plugin itself. By ensuring your plugin is updated and your cron jobs are configured properly for your site's traffic level, you can resolve these Site Health warnings.