Benjamin Intal

<p>This plugin behaves similarly to <a href="https://wordpress.org/plugins/regenerate-thumbnails/" rel="ugc">Regenerate Thumbnails</a> except that images are resized automatically / on the fly, when they are used. Once created, they won’t be processed again.</p>
<p>Your thumbnails will now resize when:</p>
<ul>
<li>Image Sizes in <strong>Settings > Media</strong> is modified,</li>
<li>Switching themes & plugins with different thumbnail / featured image sizes</li>
</ul>
<p>No settings pages, just install and activate and things should work right away.</p>
<p>Report bugs and help out in the code from the <a href="https://github.com/gambitph/WP-OTF-Regenerate-Thumbnails" rel="nofollow ugc">Github repository</a></p>
<h4>What are you talking about?</h4>
<p>Test it out. In your normal WordPress website set up, create a gallery using the <strong>Add Media</strong> button while editing a post or page and use thumbnails. Afterwards, check out your gallery.</p>
<p>Notice the size of your thumbnails, most likely they’re <strong>150 x 150</strong>. Do you see it? Great.</p>
<p>Now head over to <strong>Settings > Media</strong> and change your thumbnail size to something cooler, something rectangular, let’s try <strong>400 x 200</strong>. Save it.</p>
<p>Go back to your gallery that you previously created and refresh your browser. Most likely you <em>won’t</em> be seeing <strong>400 x 200</strong> thumbnails there.</p>
<p>OTF Regenerate Thumbnails fixes this for you.</p>
<h4>Usage</h4>
<p>OTF Regenerate Thumbnails should work right away, and your images should get resized when the dimensions get changed.</p>
<p><strong>For developers & tinkerers, ensuring your images get resized properly requires you to use WordPress’ image functions to display featured images and image attachments.</strong> Don’t worry, this is a good thing.</p>
<p>Make sure you use these WordPress functions <strong>every time you display images</strong>:</p>
<ul>
<li><a href="https://codex.wordpress.org/Function_Reference/wp_get_attachment_image_src" rel="nofollow ugc"><code>wp_get_attachment_image_src</code></a></li>
<li><a href="https://codex.wordpress.org/Function_Reference/wp_get_attachment_image" rel="nofollow ugc"><code>wp_get_attachment_image</code></a></li>
<li><a href="https://codex.wordpress.org/Function_Reference/the_post_thumbnail" rel="nofollow ugc"><code>the_post_thumbnail</code></a></li>
<li><a href="https://codex.wordpress.org/Function_Reference/get_the_post_thumbnail" rel="nofollow ugc"><code>get_the_post_thumbnail</code></a></li>
</ul>
<p>You can also add size <em>names</em> using <a href="https://codex.wordpress.org/Function_Reference/add_image_size" rel="nofollow ugc"><code>add_image_size</code></a></p>
<h4>Features</h4>
<ul>
<li>Creates Resizes thumbnails on the fly</li>
<li>Handles Image Size settings changes in <strong>Settings > Media</strong></li>
<li>Handles thumbnail / image size changes introduced by switching themes & plugins</li>
<li>Works automatically, no setup needed</li>
<li>All calls to <code>the_post_thumbnail</code> and other thumbnail functions are handled automatically</li>
<li>Handles image sizes created from <code>add_image_size</code>,</li>
<li>Handles <a href="https://codex.wordpress.org/Function_Reference/the_post_thumbnail" rel="nofollow ugc">2-item array sizes</a></li>
</ul>


OTF Regenerate Thumbnails

Front end - must have

Nice plugin, very useful.
Also works on a network install.
Thanks!



Very useful

Automatically regenerates your thumbnails on the fly when thumbnail sizes change.

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.

OTF Regenerate Thumbnails vs Thumbnail Manager