zabatonni

Automatically finds duplicate terms (with same name) in each taxonomy, then moves posts from duplicates to its original terms and deletes duplicate terms.
You can choose which duplicates you want to merge and delete.

Merge duplicate terms

Plugin for easy merging duplicate terms (tags, categories, ...)

Brave Digital

WordSync allows you to synchronise posts, pages, users, taxonomies, attachments and settings between two WordPress installs. 
After setting up the link between the two sites using a secret key, you can perform a sync on the target site which will show all changes needed to bring it’s content in sync with the source site. 
You can select which of these changes you’d like to synchronise across before the sync is performed. 
WordSync will handle updating site urls automatically, download attachments and maps users, posts and attachments from one site to the other without conflicts.
WordSync provides modular synchronisers which act on certain bits of data on your site:
<ul>
<li>Settings – syncs all WordPress settings and all plugin settings (for those plugins that store their settings in the wp_settings table)</li>
<li>Users – Creates, updates and deletes users so that they reflect the source site. New users will have to reset their passwords in order to login.</li>
<li>Posts – Synchronises ALL posts, including pages and all custom post types. Preserves post parent relationships</li>
<li>Taxonomies – Synchronises all taxonomy terms, but both sites need to have the same taxonomies defined. Ie. if the theme defines custom taxonomies, both sites must have the same theme active.</li>
<li>Attachments – Synchronises attachments. Attachment images are downloaded directly from the source site and then inserted into the media library and linked up to the same posts as in the source site.</li>
</ul>
You can choose which of these to activate before performing a sync but some rely on others to run first before they themselves are able to run.
For now WordSync transmits site data between the sites in an unencrypted stream. While eavesdropping is extremely unlikely, bear this in mind if you have sensitive data.
WordSync is designed to be used by developers and other super-users who work with WordPress sites. The plugin will expose a bit of the inner workings of WordPress to you and requires your judgement to know which data should be synced without overwriting data you’d like to keep.
<h3>** Warning **</h3>
This plugin modifies your site content and is still in alpha. It may not always perform adequately and it would be strongly advisable to backup your site before using WordSync. WordSync does not offer a rollback option once your data has been synced. Brave Digital does not accept any responsibility for lost or corrupted data. USE THIS PLUGIN AT YOUR OWN RISK.
<h3>Contribute on GitHub</h3>
Help us make improvements and additions by contributing on the WordSync GitHub project:
https://github.com/brave-digital/WordSync

WordSync

WordSync allows you to synchronise posts, pages, users, taxonomies, attachments and settings between two WordPress installs.

Merge duplicate terms vs WordSync