Unlike traditional applications, Progressive Web App can be seen as an evolving hybrid of regular web pages (or websites) and a mobile application. This new application life-cycle model combines features offered by most modern browsers with benefits of mobile experience.

Progressive Web Apps

Ice-breaking PWA

There is already a good number of articles that are dedicated on PWA. So am not getting into those here. We will directly jump to the implementation of push notification. For you to get started, I had uploaded a sample app to the git repo. We will start from there. On the other hand if you need further more details on PWA, please follow these links.

Getting started

Now lets get started with our project. First thing you need to do is clone the below project to your local machine. We will start from there.


The code base of the repo is divided into two part. Server and Client side. All the files in the server folder is of server’s file. And rest of the files belongs to client side app.

Client Side

All the code except the one in the folder server belongs to client side. The directory structure may look like this.

+-- root
| +-- images
| +-- js
| \`-- main.js
| +-- server
| -- index.html
| -- manifest.json
| -- sw.js

These are the crucial files of our application.

Now start serving the root folder with your favorite server like ngnix, python server, live-server, etc. Personally I use live-server.

npm install -g live-server

live-server --port=80

Now when you open http://localhost in your machine, you will see the PWA running. But if you examine the console, you will get an error like this

PWA Boot up

Obtaining gcm-senderId

Adding gcm-senderId to the manifest file

It is important to know that, all PWA are driven by the manifest.json file associated with it.

  • Open the manifest.json

  • You could see a field called gcm_sender_id of 12 digits.

  • Now paste the Sender Id you got from previous step here.

  • Go back to Localhost and check out your console. The previous error seems to be gone.

If the error is gone, it means your app has been subscribed to the firebase project that we created before. And it is ready to receive messages aka notifications from the cloud via firebase cloud messaging.

You might note few more key’s generated on browsers console. These are very important key’s we will be discussing it now.

Make a note of these values

  • endpoint

  • p256dh

  • auth

Encrypted Push Notification.

If you want to sent just some push notification to the client, we can do those with a POST request on POSTMAN. But if in any case we need to add payload to our notification we need to encrypt it. In any case, all the non encrypted messages will be discarded by both Chrome and Firefox, thus you may get data field as null. So we won’t be discussing the non encrypted part here.

The reason why encryption is essential because, there is no other way to identify where the message is coming and where it is going. If encryption isn’t enabled that may open couple of major security holes. Here is few interesting article from Chrome and Mozilla.

  • https://developers.google.com/web/updates/2016/03/web-push-encryption

  • https://developer.mozilla.org/en-US/docs/Web/API/Push_API

So the encryption of data will be done by using the clients p256dh and auth that we got on the console. Hope you have noted down those.

Server Side

Go to the server folder on another bash / command line. Execute the following commands.

cd server

npm install

We know that we are using encrypted messaging. In order to achieve this by hand is very difficult and time consuming. For the reason, we will be using web-push library. Its a node.js library. When you run npm install web-push will be installed on the server directory. Its very important that you should understand Why we use web-push? and How it works?.

Setting up server side key’s

Go to the file server.js. The following line numbers are to be edited

Line 10 :

webpush.setGCMAPIKey('{ { your Firebase Cloud messaging key } }');

replace { {your Firebase Cloud messaging key} } with Server Key that you got from cloud messaging tab of your firebase project.

Line 14 :


Line 23 :

replace { {client subscription id} } with endpoint you got from browser’s console

Line 25 :

replace zR1............1w== with auth value you got from browser’s console.

Line 26 :

replace BGM................................................................U0= with p256dh value you got from browse’s console.

We have to develop our own mechanism to store these data in our backend, because if you want to send push notification to a user all these keys play its role.

For more reading

Invoking your first notification.

Assuming your PWA is being served and the service worker for the PWA is alive on the browser, we can trigger our first notification. All you have to do is

node server.js

If everything was implemented correctly you will get your first notification. And the data from the server will be visible in the push notification.


As I said, its not that easy to implement push notification. There are billions of notifications passing through the cloud each day. Targeting a specific user is an important thing here. The server.js file will shows the least thing you need in the back end to trigger a notification. You might see something like vapidKeys, these are the one’s which encrypts the data. In the long run, PWA is gonna rule the web, and the standardization is yet a question mark. Down the road the methods might change, yet we cant leave it and lag behind. Incase of any queries feel free to reach me on twitter


  • https://developer.mozilla.org/en-US/docs/Web/API/Push_API
  • https://developers.google.com/web/updates/2016/03/web-push-encryption
  • https://tools.ietf.org/html/draft-thomson-webpush-encryption-01
  • https://developers.google.com/web/fundamentals/getting-started/push-notifications/?hl=en
  • http://www.html5rocks.com/en/tutorials/service-worker/introduction/