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>
WP-CLI commands are available. 
* <code>wp bgth_cli mail</code> -> Send results via email. 
* <code>wp bgth_cli nomail</code> -> Do not send results by email. 
* <code>wp bgth_cli mail --uid=13</code> -> Process only specified User ID(13). 
* <code>wp bgth_cli mail --pid=12152</code> -> Process only specified Post ID(12152).

Bulk Generate Thumbnails

YoOhw Studio

Thumbnail Manager helps you take back disk space from oversized Media Libraries.
What it does 
– Prune Files: Select the image sizes you want to KEEP. The plugin scans your <code>/uploads/</code> folder and targets all non-selected registered sizes for removal. It shows a dry-run summary first, then lets you delete in batches with a live progress bar. 
– Orphan discovery: Finds on-disk files that match <code>-WxH</code> patterns (including <code>.jpg.webp</code>, <code>.bak.jpg</code>, retina <code>@2x</code>, and duplicate <code>-1</code> suffixes) even if those sizes are no longer registered. Aggressively deletes any <code>-WxH</code> files that don’t exactly match the sizes you chose to keep (use with care). 
– Subfolder scope: Limit scans to a specific year/month inside <code>uploads/</code> for faster, safer runs on large libraries. 
– Thumbnail Sizes: Choose which sizes should be generated for future uploads. Disabled sizes won’t be created at upload time (and are hidden from size pickers).
What it doesn’t do 
– It does not regenerate thumbnails. Use a regeneration plugin if you need to rebuild sizes after changing settings. 
– It never deletes original full-size images.
Who is it for? 
Site owners, editors, and developers who’ve accumulated many custom image sizes (themes, page builders, sliders) and want to reduce storage bloat safely.
<h3>Features</h3>
<ul>
<li>Two-tab UI: Prune Files & Thumbnail Sizes</li>
<li>Dry-run mode with sample matches before any deletion</li>
<li>AJAX progress bar and batch deletes to avoid timeouts</li>
<li>Orphan <code>-WxH</code> discovery report and delete found dimensions</li>
<li>Limit to subfolder (All, year, or year/month)</li>
<li>Disable sizes for future uploads (does not unregister core sizes; simply prevents generation)</li>
<li>Hides disabled sizes from Media size dropdowns (optional filter)</li>
<li>Works per-site on single and multisite (run on each site as needed)</li>
</ul>
<h3>Usage</h3>
<h3>Prune Files</h3>
<ol>
<li>In the table, check the sizes you want to KEEP (e.g., <code>thumbnail</code>, <code>medium</code>, <code>large</code>, and optionally <code>medium_large</code>).</li>
<li>(Optional) Choose a subfolder (e.g., <code>2024/11</code>) for a quicker, safer trial run.</li>
<li>Make Orphan discovery ON to see a report or do a deletion of found dimensions.</li>
<li>Click Run with Dry-run selected to preview matches.</li>
<li>Review results → switch to Delete when you’re confident.</li>
</ol>
Tip: Enable Orphan discovery only when you want to remove any extra <code>-WxH</code> sizes not exactly matching your KEEP list (great for cleaning legacy sizes like <code>-1200x860</code> or <code>.bak.jpg</code> files).
<h3>Thumbnail Sizes</h3>
<ol>
<li>Uncheck any sizes you no longer want generated for future uploads.</li>
<li>Click Save changes. 
(This prevents those sizes from being created going forward; existing files are unaffected until you prune them in Prune Files Tab.)</li>
</ol>
<h3>Technical Notes</h3>
<ul>
<li>Prevent generation via: <code>intermediate_image_sizes_advanced</code> (removes disabled sizes at upload time). </li>
<li>Optionally hide in UI via: <code>image_size_names_choose</code> and reduce the base list via <code>intermediate_image_sizes</code>. </li>
<li>Auto-scaled big image can be disabled with <code>big_image_size_threshold</code> if desired (not enabled by default). </li>
<li>Requires capability <code>manage_options</code>.</li>
</ul>
<h3>Privacy</h3>
This plugin does not collect personal data or send data to external services. It only reads and modifies files within your <code>/uploads/</code> directory based on your actions.

Thumbnail Manager

Clean up unused thumbnails with progress; find orphan -WxH files; disable sizes for future uploads.

Bulk Generate Thumbnails vs Thumbnail Manager