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.

Adi Glibanović

<p>The Selective Thumbnail Regenerator plugin provides a powerful and user-friendly way to regenerate image thumbnails for WordPress media libraries. Unlike other thumbnail regeneration plugins that blindly process the entire library, this plugin gives you precise control: choose a specific year, month, and even a title keyword to target exactly the images you need.</p>
<h4>Key Features</h4>
<ul>
<li><strong>Date & Title Filters</strong> – Choose a specific year, month, or search by title to target only the images you need.</li>
<li><strong>Month Status Calendar</strong> – A visual 4×3 calendar grid appears when you select a year. Months that have been regenerated are highlighted in green with a checkmark. Clicking a month badge automatically selects it.</li>
<li><strong>Regeneration History Tracking</strong> – Completed months are stored in the database and persist across sessions. A “Reset History” button clears all records when needed.</li>
<li><strong>Thumbnail Size Selection</strong> – Choose specific registered thumbnail sizes to regenerate instead of all sizes.</li>
<li><strong>Configurable Batch Size</strong> – Set how many images are processed per AJAX request (1-20).</li>
<li><strong>Throttle Delay Control</strong> – Set a cooldown pause between batches (0-2000 ms) to reduce server load.</li>
<li><strong>Dry Run Mode</strong> – Preview which images would be processed without writing any changes to disk.</li>
<li><strong>Automatic Batch Failure Recovery</strong> – If a batch crashes, the plugin retries each image individually, isolates the bad one, logs it, and continues with the rest.</li>
<li><strong>Failed Images Log</strong> – Detailed table of all failed images including ID, title, and exact failure reason.</li>
<li><strong>Orphaned File Cleanup</strong> – Old thumbnail files are deleted from disk before new ones are generated.</li>
<li><strong>Live Terminal Activity Log</strong> – Real-time monospace console with timestamped status messages.</li>
<li><strong>Visual Completion Metrics</strong> – Five-card summary board: Processed, Successful, Failed, Skipped, Duration.</li>
<li><strong>Cancel Support</strong> – Stop the regeneration at any time with a graceful shutdown.</li>
<li><strong>Performance Optimized</strong> – Direct indexed SQL query for year selector loading.</li>
</ul>
<h3>Usage</h3>
<ol>
<li>Navigate to Tools > Selective Thumbnail Regenerator.</li>
<li>Select a year from the dropdown. A Month Status Calendar will appear showing which months have already been regenerated.</li>
<li>Optionally select a month – via the dropdown or by clicking a month badge on the calendar.</li>
<li>Optionally enter a title keyword to filter images by name.</li>
<li>Adjust batch size and throttle delay in the Performance Configuration card.</li>
<li>Enable Dry Run Mode to preview results without making changes.</li>
<li>Click “Scan Matching Images” to count how many images match your filters.</li>
<li>Click “Start Regeneration” to begin. Watch the live terminal log for real-time updates.</li>
<li>Review the Job Completion Report and Failed Images Log after the process ends.</li>
</ol>
<h3>Troubleshooting</h3>
<h4>“No images found for the selected period”</h4>
<p>There are no image attachments uploaded during the selected year/month. Try a different time period.</p>
<h4>The process is slow</h4>
<p>Reduce the throttle delay or increase the batch size if your server can handle more load. Alternatively, increase the delay and reduce batch size if you are getting timeouts.</p>
<h4>A batch keeps failing</h4>
<p>Enable Dry Run Mode first to verify image accessibility. If specific images crash the server, they will appear in the Failed Images Log after regeneration completes.</p>


Selective Thumbnail Regenerator

Regenerate thumbnails selectively by upload date and search filters with full history calendar, performance throttle, and fail-safe recovery.

OTF Regenerate Thumbnails vs Selective Thumbnail Regenerator