Jordy Meow

When you insert images in WordPress, it’s always a specific image size. It can be an image size such as Medium, Large or something else set by your theme or another plugin. When you update your media sizes settings (or switch theme), you need to regenerate those images (with Regenerate Thumbnails, for example). But what about your posts content? They will be still using the old images, which aren’t actually part of the new metadata, and little by little your WordPress will become more and more broken. This plugin fixes this by regenerating the HTML for your thumbnails / images in your content and keeps everything clean. Once this is done, it’s a good idea to run a tool like Media Cleaner (https://wordpress.org/plugins/media-cleaner/) on your install to detect the useless files.
Be careful!. Before using this plugin, backup your database! It doesn’t modify your files, only database.

Regenerate Thumbnails HTML

Works well on my two plugins after switching to a new theme. Regenerate Thumbnails (after set up the new sizes) + Regenerate Thumbnails HTML (on all posts, for 2 or 3 sizes) + Media Cleaner (to delete the useless files). In one hour, the new installs are neat and clean.

It works well

Thank you!
After change WP media sizes for new theme we must use regenerate thumbnail plug-in. But I want apply new sizes in old post! After that I can clear old images!

Good work with "view-broken-links" plug-in.

Gold in ocean of wp problems

Update the HTML of the images contained in the post from one image size to another. Useful when switching between sizes and themes.

thaikolja

Thumbnails Cleaner helps you keep your WordPress installation tidy by removing and regenerating thumbnails.
You can control all functions through the plugins’ main page found under “Tools”. You can:
<ul>
<li>Analyze your uploads directory, giving you an overview how many original files and thumbnails there are.</li>
<li>Clean thumbnails which means deleting them while keeping the original files.</li>
<li>Restore thumbnails to start out with a clean uploads directory. This function requires the plugin <a href="https://wordpress.org/plugins/regenerate-thumbnails/" rel="ugc">Regenerate Thumbnails</a>.</li>
<li>Create backups of your uploads directory to keep your files safe in the unlikely event that there is a problem.</li>
<li>Restore backups in case you have lost a file that was not supposed to be deleted.</li>
</ul>
Please see the <a href="https://www.koljanolte.com/wordpress/plugins/thumbnail-cleaner/documentation/" rel="nofollow ugc">official website</a> for a full 
documentation.

Thumbnail Cleaner

Cleans up your WordPress installation by removing and regenerating thumbnails.

Regenerate Thumbnails HTML vs Thumbnail Cleaner