[ios] How can a web application send push notifications to iOS devices?

I'm working on a web app. How can I send push notifications to iOS users when there is new content?

The W3C started in 2010 a working group to implement notifications:
http://www.w3.org/2010/web-notifications/

This Working Group develops APIs that expose those mechanisms to Web Applications—so that Web developers creating, for example, Web-based e-mail clients and instant-messaging clients can more closely integrate their Web application behavior with the notification features of the operating systems of their end users.

Finally the result is like a bad joke as it works only if the specific website is open: http://alxgbsn.co.uk/notify.js/

I think they missed to implement the possibility to add push urls so the browser is able to ask for notifications while its running in the background - and above all - if all tabs have been closed.

ACTUALLY.. This is brand new mind you.. On the newest version of OS X (Mavericks) you CAN send push notifications from a webpage to the desktop. But according to the documentation, NOT iPhones:

Note: This document pertains to OS X only. Notifications for websites do not appear on iOS.

Currently Apple has plans to allow 2 kinds of push notifications: OS X Website Push Notifications and Local Notifications.

The obvious hurdle here is that this will not work on PCs, nor will it allow you to do android push notifications.

Furthermore, you actually can with versions as old as Snow Leapord, send push notifications from a website as long as said website is open and active. The new Mavericks OS will allow push notifications even if the site isnt opened, assuming you have already given permission to said site to send push notifications.

From the mouth of Apple:

In OS X v10.9 and later, you can dispatch OS X Website Push Notifications from your web server directly to OS X users by using the Apple Push Notification service (APNs). Not to be confused with local notifications, push notifications can reach your users regardless of whether your website or their web browser is open…

To integrate push notifications in your website, you first present an interface that allows the user to opt in to receive notifications. If the user consents, Safari contacts your website requesting its credentials in the form of a file called a push package. The push package also contains notification assets used throughout OS X and data used to communicate to a web service you configure. If the push package is valid, you receive a unique identifier for the user on the device known as a device token. The user receives the notification when you send the combination of this device token and your message, or payload, to APNs.

Upon receiving the notification, the user can click on it to open a webpage of your choosing in the user’s default browser.

Note: If you need a refresher on APNs, read the “Apple Push Notification Service” chapter in Local and Push Notification Programming Guide. Although the document is specific to iOS and OS X push notifications, paradigms of the push notification service still apply.

Google Chrome now supports the W3C standard for push notifications.

http://www.w3.org/TR/push-api/

While not yet supported on iOS (as of iOS 10), websites can send push notifications to Firefox and Chrome (Desktop/Android) with the Push API.

The Push API is used in conjunction with the older Web Notifications to display the message. The advantage is that the Push API allow the notification to be delivered even when the user is not surfing your website, because they are built upon Service Workers (scripts that are registered by the browser and can be executed in background at a later time even after your user has left your website).

The process of sending a notification involves the following:

1. a user visits your website (must be secured over HTTPS): you ask permission to display push notifications and you register a service worker (a script that will be executed when a push notification is received)
2. if the user has granted permission, you can read the device token (endpoint) which should be sent to the server and stored
3. now you can send notifications to the user: your server makes an HTTP POST request to the endpoint (which is an URL that contains the device token). The server which receives the request is owned by the browser manufacturer (e.g. Google, Mozilla): the browser is constantly connected to it and can read the incoming notifications.
4. when the user browser receives a notification executes the service worker, which is responsible for managing the event, retrieving the notification data from the server and displaying the notification to the user

The Push API is currently supported on desktop and Android by Chrome, Firefox and Opera.

You can also send push notifications to Apple / Safari desktop using APNs. The approach is similar, but with many complications (apple developer certificates, push packages, low-level TCP connection to APNs).

If you want to implement the push notifications by yourself start with these tutorials:

• Push API: Push Notifications on the Open Web
• Apple Push Notification system: Configuring Safari Push Notifications

If you are looking for a drop in solution I would suggest Pushpad, which is a service I have built.

Update (September 2017): Apple has started developing the service workers for WebKit (status). Since the service workers are a fundamental technology for web push, this is a big step forward.

Check out Xtify Web Push notifications. http://getreactor.xtify.com/ This tool allows you to push content onto a webpage and target visitors as well as trigger messages based on browser DOM events. It's designed specifically with mobile in mind.

You can use pushover if you don't want to create your own native app: https://pushover.net/

No, there is no way for an webapp to receive push notification. What you could do is to wrap your webapp into a native app which has push notifications.

You can use HTML5 Websockets to introduce your own push messages. From Wikipedia:

"For the client side, WebSocket was to be implemented in Firefox 4, Google Chrome 4, Opera 11, and Safari 5, as well as the mobile version of Safari in iOS 4.2. Also the BlackBerry Browser in OS7 supports WebSockets."

To do this, you need your own provider server to push the messages to the clients.
If you want to use APN (Apple Push Notification) or C2DM (Cloud to Device Message), you must have a native application which must be downloaded through the online store.

No, only native iOS applications support push notifications.

UPDATE:
Mac OS X 10.9 & Safari 7 websites can now also send push notifications, but this still does not apply to iOS. Read the Notification Programming Guide for Websites. Also check out WWDC 2013 Session 614.

Pushbullet is a great alternative for this.

However the user needs to have a Pushbullet account and the app installed (iOS, Android) or plugin installed (Chrome, Opera, Firefox and Windows).

You can use the API by creating a Pushbullet app, and connect your application's user to the Pushbullet user using oAuth2.

Using a library would make it much easier, for PHP I could recommend ivkos/Pushbullet-for-PHP.