Katsushi Kawamori

<h4>Generate Thumbnails</h4>
<ul>
<li>Generate Thumbnails from all the images by asynchronous processing.</li>
<li>Generate Thumbnails from select the images by asynchronous processing.</li>
<li>If you are an administrator, it will generate thumbnails for all images, otherwise it will generate thumbnails for the images owned by each user.</li>
</ul>
<h4>The following plugin adds a function for generating thumbnails.</h4>
<ul>
<li>Select the thumbnails and functions to disable it. <a href="https://wordpress.org/plugins/disable-generate-thumbnails/" rel="ugc">Disable Generate Thumbnails</a></li>
<li>Specify the ratio of thumbnails generation. <a href="https://wordpress.org/plugins/ratio-thumbnails-size/" rel="ugc">Ratio Thumbnails Size</a></li>
</ul>
<h4>WP-CLI</h4>
<p>WP-CLI commands are available.<br />
* <code>wp bgth_cli mail</code> -> Send results via email.<br />
* <code>wp bgth_cli nomail</code> -> Do not send results by email.<br />
* <code>wp bgth_cli mail --uid=13</code> -> Process only specified User ID(13).<br />
* <code>wp bgth_cli mail --pid=12152</code> -> Process only specified Post ID(12152).</p>


Bulk Generate Thumbnails

YoOhw Studio

<p>Thumbnail Manager helps you control WordPress thumbnail generation, regenerate image sizes, and clean unused thumbnail files from the Media Library.</p>
<p>Use it after changing themes, installing WooCommerce, disabling custom image sizes, or cleaning up years of generated media files. The plugin focuses on predictable thumbnail management: choose which image sizes should stay enabled, rebuild the thumbnails you need, preview cleanup results, then delete only reviewed generated files.</p>
<p>Cleanup is metadata-aware and safety-focused. Thumbnail Manager validates uploads paths, protects original full-size images, runs prune/delete actions in batches, and updates attachment metadata after deleted thumbnail sizes are removed.</p>
<h4>Key Features</h4>
<ul>
<li>Regenerate WordPress thumbnails for existing image attachments</li>
<li>Generate only missing thumbnails or force-regenerate all selected images</li>
<li>Disable unwanted registered image sizes for future uploads</li>
<li>Prune unused thumbnails while keeping selected sizes</li>
<li>Run Dry-run previews before deleting generated thumbnail files</li>
<li>Detect legacy thumbnail sizes stored in attachment metadata</li>
<li>Report disk-only orphan matches without deleting unmapped files by default</li>
<li>Scan recommendations based on protected sizes, WooCommerce-related sizes, generated metadata, and common content references</li>
<li>Process large Media Libraries with cursor-based AJAX queues and folder scoping</li>
<li>Manage everything from Tools > Thumbnail Manager</li>
</ul>
<h4>Common Use Cases</h4>
<ul>
<li>Clean WordPress thumbnail bloat after theme or page builder changes</li>
<li>Regenerate thumbnails after changing Media Settings or custom image sizes</li>
<li>Reduce WooCommerce image storage by reviewing generated product thumbnails</li>
<li>Disable image sizes that should no longer be created for new uploads</li>
<li>Rebuild missing thumbnails after migration, restore, or failed image processing</li>
<li>Audit legacy thumbnail sizes left behind by old themes and plugins</li>
</ul>
<h4>Safety First</h4>
<p>Thumbnail Manager is designed for controlled cleanup, not blind filesystem deletion.</p>
<ul>
<li>Original full-size images are not deleted</li>
<li>Delete mode requires a fresh delete token and a completed scan</li>
<li>Dry-run mode never deletes files</li>
<li>Cleanup targets files from attachment metadata</li>
<li>Disk-only orphan matches are reported, not deleted by default</li>
<li>Paths are validated under the WordPress uploads directory before deletion</li>
<li>Attachment metadata is updated after generated thumbnail sizes are removed</li>
</ul>
<h4>What It Does Not Do</h4>
<ul>
<li>It does not compress or optimize image quality</li>
<li>It does not replace image optimization or CDN plugins</li>
<li>It does not automatically delete media without confirmation</li>
<li>It does not delete original uploaded images</li>
<li>It does not unregister image sizes from themes or plugins</li>
</ul>
<h3>Usage</h3>
<h4>Recommended Workflow</h4>
<ol>
<li>Open Tools > Thumbnail Manager.</li>
<li>Scan Recommendations to review likely keep/remove sizes.</li>
<li>Apply recommended sizes if they match your site.</li>
<li>Open Thumbnail Sizes and save the sizes you want generated for future uploads.</li>
<li>Run Regenerate to rebuild missing or selected thumbnails.</li>
<li>Open Prune Files and run Dry-run before any deletion.</li>
<li>Review matched files, then switch to Delete only when the preview is correct.</li>
</ol>
<h4>Regenerate Thumbnails</h4>
<p>Use Regenerate when you need to rebuild WordPress image sizes for existing attachments. You can process all media, the current year, a specific uploads folder, or specific attachment IDs.</p>
<h4>Prune Files</h4>
<p>Use Prune Files to clean generated thumbnails for sizes you no longer want to keep. Always run Dry-run first. If orphan discovery is enabled, metadata-backed legacy sizes can be included, while unmapped disk-only matches are reported for review.</p>
<h4>Thumbnail Sizes</h4>
<p>Use Thumbnail Sizes to control which registered image sizes WordPress should generate for future uploads. This setting does not remove existing files until you run Prune Files.</p>
<h3>Technical Notes</h3>
<ul>
<li>Uses <code>intermediate_image_sizes_advanced</code> to control future thumbnail generation</li>
<li>Uses cursor-based AJAX queues for regenerate and prune scans</li>
<li>Uses attachment metadata for prune candidates</li>
<li>Validates filesystem paths under the uploads directory before deletion</li>
<li>Updates attachment metadata after generated thumbnail files are removed</li>
<li>Requires the <code>manage_options</code> capability</li>
<li>Works per site on multisite installations</li>
</ul>
<h3>Privacy</h3>
<p>Thumbnail Manager does not collect, store, or transmit personal data. All thumbnail scans, regeneration actions, and cleanup actions run locally on your WordPress site.</p>


Thumbnail Manager

Regenerate WordPress thumbnails, disable image sizes, and safely clean unused media library thumbnails with dry-run previews.

Bulk Generate Thumbnails vs Thumbnail Manager