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Mustafa Uysal

AppThemes

On a multisite installation, the admin bar has a menu item called My Sites.
If you’re not a big fan of the admin bar on the front-end, try this widget instead. If the user is not logged in, he won’t see the widget at all.

My Sites Widget

A widget that displays a list of sites that the current user has access to.

Emanuela Castorina

This plugin in a multisite installation shows the ID of the current site/blog in the admin bar menu. The ID of the current site/blog is linked to the site info page. 
It adds also a custom column with site id information inside the sites list table. 
It can be installed only on a multisite.

Wp Show Site ID

This plugin in a multisite installation shows the ID of the current site/blog.

My Sites Widget vs Wp Show Site ID