Mario Peshev

Delete all Custom Field entries assigned to posts that do not exist in the posts table.
Navigate to Settings -> Remove Unused CFs and delete all postmeta for non-existing posts.

DX Remove Unused Custom Fields

Does exactly what it says.
Installed, navigate to the settings page, click "Delete" and Done! Cannot be easier than that.
Thank you!



Simply Awesome!

Delete the Custom Fields from your postmeta table where assigned posts no longer exist.

Delete the posts from Custom Post Types that are no longer active for the install.
Navigate to Settings -> Remove Oldies and delete the posts from a given post type that is not active anymore.

DX Remove Oldies

Delete the posts from Custom Post Types that are no longer active for the install.

DX Remove Unused Custom Fields vs DX Remove Oldies