Since the introduction of the Safari browser of the Mavericks version of Mac OSX, and also recently in Chrome for Mac, your website may show Desktop notices to encourage your readers to receive notices on your computer, even if they do not have the web browser open .
This thing called Web Push Notifications is a subscription system to the news of a really interesting website, because when you publish new content the user will receive a warning of their operating system, even if they do not have the web browser open being able to check the last of your site.
- Settings notifications Safari  Mac notifications settings
- Mac notifications center
What's more, there are some systems that allow you to send personalized notices, not just the automatic ones that are generated every time you publish a new entry.
And the best thing of all is that there are a lot of free services that allow to integrate this system of Web Push Notifications in WordPress through plugins. Let's see some …
Really simple, just install it and add a new icon to the desktop menu of WordPress from which you access the web service of Tidio from where configure the appearance of the subscription and desktop notices. It also allows sending personalized messages.
For Chrome notifications it is necessary to upload a file to your server via FTP, due to the requirement that they are HTTPS connections.
All simple and all for free .  OneSignal Web Push Notifications
This plugin links to OneSignal, a service that connects to the Google Developer Console so that, once registered (free) in OneSignal, you create an application that activates the desktop web ads.
A little bit more cumbersome to start up than the previous one but equally very effective and also free .
Another service that offers us, through a plugin, the creation of web notifications is that of Push Monkey. Once installed the plugin automatically invites us to its settings page, which encourages us to create an account, which will offer us a trial service for 30 days, or if we prefer one of the payment plans, ranging from $ 2.5 a month, you decide, but the good thing is that you can try it before.
The system is very easy to configure, has statistics and works great.
One of the most used, the Roost web notification system also goes through the registration in their service, offering notices in Safari and Chrome, plus a lot more options.
Like the previous one, just install the plugin invites us to create a 30-day trial account in the service before using it, with the proviso that you will ask us for the credit card information, even if they do not load anything initially.
The good news is that you can skip this step , so if you leave the proces or register in that step and go back to your WordPress you will see that you can access with the chosen email and password and use it without needing to give any banking information.
From the plugin's administration page you have access to the settings, where you can even specify the sending of notices when there are new messages in bbPress forums, what categories will send notifications, and if you prefer to send the notification only when a user visits you more than once or only after clicking on something, not to be especially heavy.
Of course, as a professional service that is, you can also send personalized notices, not just the automatic ones when you post something, a great marketing element.
Which is better?
It's a complicated question. Actually the best is the Roost system and in fact the most used professionally. Now, if for you it is a problem the monthly payment for a service for a limited user segment (Mac users) perhaps your best choice is one of the first two, among which wins by a landslide in simplicity Tidio system the plugin called Web Push Notifications simpler is impossible.
Above all keep in mind what I just pointed out, that is something that you offer to a very specific sector of visitors, those who use Safari or Chrome for Mac who will be the ones who will really take advantage of this type of notification service.
Yes, you will mark differences completely, because it does not stop being a really powerful subscription service, that warns your readers even if they do not have the browser open, directly on their computer desktop .
Note: Web notifications only work with the web browser S afari for Mac OSX and Chrome for Mac OSX, and in the case of Chrome only with HTTPS.