As a website owner you will need to know how popular and visited your site is, so the statistics of the site visits and online visitors will be essential for you. For this Visitors online plugin is all you really need. Simple, but at the same time very helpful Visitors online allows you to track the statistics of users, guests, and bots online and to see the number of visits in the past. Moreover, you will know what browsers are/were used and what countries are visiting or visited your website.
So you will see the visitor online even if the user has already left the site, but the set time of being online is not over yet.