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

mansoormunib

<p>Image Sizes in Admin Dashboard adds a read-only widget to the WordPress admin Dashboard that lists all currently registered image sizes.</p>
<p>Any size you register in your theme or plugin with <code>add_image_size()</code> is picked up automatically, alongside the built-in <code>thumbnail</code>, <code>medium</code>, <code>medium_large</code> and <code>large</code> sizes. Each row shows:</p>
<ul>
<li>The image size name (human readable)</li>
<li>Width in pixels (— when unconstrained)</li>
<li>Height in pixels (— when unconstrained)</li>
<li>Crop mode (Cropped or Proportional)</li>
</ul>
<p>This is handy when building a theme and you need a quick reference of the exact dimensions available to <code>the_post_thumbnail()</code> and the media library.</p>
<p>More detail on registering custom image sizes: https://developer.wordpress.org/reference/functions/add_image_size/</p>


Image Sizes in Admin Dashboard

....

Lists every registered image size — built-in and custom add_image_size() sizes — with width, height and crop mode in a Dashboard widget.

Bulk Generate Thumbnails vs Image Sizes in Admin Dashboard