<h3>What does it do?</h3>
This plugin does nothing else than to use the internal export function of ACF to filter the data from your main page. After that all fieldgroups of your subpage will be deleted and re-imported. So it’s more of a hack than a real sync.
This has the consequence that the ID integer of your posts shoots pretty in height with frequent use. But that doesn’t really matter I think.

Advanced Custom Fields: Multisite Sync

Sync your Advanced Custom Fields to all of your multisite installations with just one click. Needs ACF Pro 5.0+

Konrád Koller

This plugin helps you to fix any missing thumbnail issue in a fairly short time. The only thing you need to do is just few simple click and the plugin does the rest. It can be really helpful if you have thousands of images in your database.
You can regenerate thumbnails for each single image in your database or you can simply select those you really want to update. If you choose a post or page the plugin will regenerate thumbnails for each related images. You can choose from the following methods:
<ul>
<li>Regenerate thumbnails for all images in the database.</li>
<li>Bulk action in post liste: You can choose which one to update by checking the checkboxes.</li>
<li>Media library items: Move your mouse over the chosen image(s) and click on “Regenerate thumbnails” link.</li>
<li>Post editor: click on “Regenerate thumbnails” button which is next to “Add media” button. (Off by default)</li>
</ul>
Furthermore you can add your own thumbnails sizes, change default JPG compression rate and mass regenerate thumbnails. The best thing about this plugin is that you can use it with custom post types as well.

ONet Regenerate Thumbnails

Doesnt have 4.4.1 bulk generation support. But you can generate thumbnails one by one.



Doesnt have 4.4.1 support completely

Fix missing thumbnails in no time with few easy clicks. The plugin does the hard work.

Advanced Custom Fields: Multisite Sync vs ONet Regenerate Thumbnails