How to put notifications in Title? [duplicate]

You can do this by using a function in javascript :

function changeTitle() {
    var titulo = document.title;
    var numero = 5; // Número de notificações a ser exibidas
    var novoTitulo = '(' + numero + ') ' + titulo;
    document.title = novoTitulo;
}

It depends on you to change the numero variable to get the amount of notifications your user has.

In the case of facebook and many other sites that use this technique, the result is obtained through reactive frameworks, example React , Vue , etc ...

in the title tag has the following

<title>{{notificações}} Facebook</title>

If WebSocket detects a new notification, the "notifications" interpolation will update with the correct value, this concept is called Two way data binding