Out of the box, a WordPress Multisite network keeps its users and its sites apart: a new user joins no site, a new site starts with nobody but its administrator, and a role changed on one site stays there. DiluxOne Multisite User Sync closes that gap from Network Admin.

Formerly WPM User Sync: same plugin, same settings, a new name in the DiluxOne family.

Three automatic triggers, each one on or off

New user: a user added to the network (by a super admin, by registration, or by another plugin) joins every site, with each site’s default role.
New site: a new site gets every user of the network, with the new site’s own default role.
Role change: a role changed on one site is copied to the other sites the user already belongs to, where that role exists. Administrator is never copied.

Two manual actions

Sync from scratch: every user to every site, or only to the sites you tick. Existing memberships are never changed.
Add back people who were removed, only if you tick the box: someone an administrator removed from a site stays off it otherwise, whatever the triggers say.

Safe by default

Super admins are never added as members (they reach every site already), and archived, spam and deleted sites are left alone.
Only super admins see the plugin. A site’s own administrator cannot pull the network’s users into their site.
Big networks: a sync too large for one request runs in the background through WP-Cron, in batches, with its progress on the Network Sync Actions screen.
Users are never duplicated: one account, added to more sites. Uninstalling removes the plugin’s settings and keeps every membership.

Works on any WordPress Multisite host.

For developers

Filters: wpmus_excluded_site_ids (sites the sync never writes to), wpmus_should_sync_user (skip one user on one site), wpmus_replicate_role (which roles the role trigger copies), wpmus_sync_inline_limit, wpmus_sync_batch_size and wpmus_sync_time_limit (how big syncs are split). The source, its tests and the whole list are on GitHub: https://github.com/DiluxOne/diluxone-multisite-user-sync-wordpress