Browser support for web push notifications
Pushpad uses a very recent technology for web push notifications: it's called the Push API and currently is supported by the latest versions of Chrome (desktop and Android), Firefox (desktop and Android), Edge (Windows) and Opera. Pushpad also uses the proprietary Apple Push Notification system to support Safari push notifications on desktop.
Notifications are delivered immediately even when the user is not surfing your website. Chrome for Android, Edge and Safari deliver the notifications even when the browser is closed, while Firefox and Chrome on desktop need to be open (otherwise the notifications will be delivered as soon as the user opens the browser).