Webhooks: Push Notifications for Blockchain Events

Real-time notifications for events on the blockchain, also known as webhooks, are vital for users of all sorts of dApps, from crypto exchanges, marketplaces, crypto payment applications or any other sort of DeFi app. 

If you’re managing a crypto project or you’re interested in building a decentralized application on Ethereum, Binance Smart Chain or any other smart contract enabled blockchain, then it’s likely you need this one essential feature for notifications.  

Adding a webhook feature to your dApp can automatically and immediately notify your users of all sorts of critical events on the blockchain. Events can include instances such as when their trades are executed, transactions fail, or if their NFT auction bid has been accepted.  

Without this information users can end up missing out on crucial trades and lucrative deals, and they could abandon your dApp for one that allows them to better manage their digital assets.  

Unfortunately, building webhooks into a dApp can be complicated and time-consuming. It also requires a steep learning curve and has plenty of opportunities for human errors and technical bugs along the way.  

That's why Crypto APIs has included Blockchain Events into our product suite, allowing businesses to easily integrate, set up and send real-time notifications to their users.  

What are Webhooks? 

In simple terms, webhooks are automatically configured notifications that instantly transmit information from one source to another, only when a specific event takes place.  

In technical terms, they are described as "user-defined callbacks made with HTTP". 

Instead of data and executable commands sent through the command line in your computer, webhooks are sent from one app to another over HTTP. 

They are software “hooks” that work over the web and only run when something happens.  

They are a more efficient version than polling that uses the pull model of communication. Polling requests made by a client are when one system pulls the information from another. 

Webhooks, on the other hand, use a push model. The requests are made by a server, and the information is pushed from a source application to a destination application. 

Let’s take a real-world analogy of the postal service... 

Polling would require you (the client) going to the post office every day and asking if they have mail for you.  

Webhooks are the postal worker (server) pushing the mail though your letterbox only when there is something to deliver. 

Instead of continuously polling the server to find out if the state has changed or the event has occurred, webhooks provide information only if and when it happens and becomes available. 

In this way, webhooks are a much more efficient system for developers. 

How do Webhooks Work?   

Webhooks work in a similar way to push notifications that pop-up on your smartphone from your applications. For example, if you make a payment with your digital banking credit card, the banking app will “push” a pop-up message within 1-2 seconds, informing you about a transaction.  

A webhook is initiated by registering a URL (verified domain) to send notifications to once certain events occur. This is known as the action application’s webhook URL. It’s the application you want to do something based on the data it will receive.   

An action application sends an HTTP request to a trigger application and when an event happens on the trigger application, it serializes the event data and sends it to the action application’s webhook URL. 

The Benefits of Webhooks for dApps 

Webhooks make receiving information in real-time much more efficient and cut out the need for constant requests, as is necessary with polling. 

For the blockchain, webhooks greatly simplify obtaining information on cryptocurrency price changes, confirming transactions, and receiving funds, all of which can aid in user account management.  

Use Cases of Blockchain Events 

There are many crypto and blockchain related businesses that rely on webhooks to deliver instant alerts on account changes and other events on the blockchain. 

For example: Crypto Exchanges, Crypto Wallets, Block Explorers, Digital Banks, Portfolio Tracking Apps, Crypto Taxes & Accounting, Hardware Wallets and more.

How to Set Up a Webhook with Crypto APIs 

Notifications can be set for various events/endpoints across Crypto APIs’ products such as Blockchain Events and Blockchain Automations (for both tokens and coins forwarding).

To be able to successfully subscribe to an event and set up a notification webhook (also known as a callback) follow these simple steps: 

1. Verify a domain in your Crypto APIs Dashboard. This will be used to base the Callback URL on, so that you can receive the Callback. 

 *Crypto APIs will notify the user with a callback only when a specific event occurs. There are often cases when an event doesn't happen at all, or takes a long time to do so. A callback notification will not be sent if the event does not or cannot occur. 

2. Set up your preferred Callback by subscribing to a chosen event through our API. 

3. If all criteria are met and the event occurs, a Callback will be received to the user’s Callback URL. 

Check out our technical guidelines on how to set up your callbacks on the Crypto APIs 2.0 Dashboard. 

Webhooks Available with Crypto APIs 

Simply put, a blockchain “event” is something that occurs on the blockchain or on the crypto market. Currently Crypto APIs offers certain Blockchain Event endpoints. You can subscribe for one, a few, or all of them, and receive callback notifications when a specific event occurs.   

• New unconfirmed coins transactions - There are new unconfirmed coin transactions for the user.  
  
• New unconfirmed tokens transactions - There are new unconfirmed tokens transactions for the user.  
  
• New confirmed coins transactions - There are new incoming or outgoing confirmed transactions for coins from/to the customer's address. 
• New confirmed tokens transactions - There are new incoming or outgoing confirmed transactions for tokens from/to the customer's address. 
  
• New confirmed tokens transactions and each confirmation - There are new incoming or outgoing confirmed transactions for tokens from/to the customer's address with also a response at each confirmation the transaction has received until the specified confirmations limit is reached. 
• New confirmed coins transactions and each confirmation - There are new incoming or outgoing confirmed transactions for coins from/to the customer's address with also a response at each confirmation the transaction has received until the specified confirmations limit is reached.
• Mined transaction - The event is when a specific transaction is mined.
  
• New block - The event is when a new block is mined in a specific blockchain. 
• New confirmed internal transactions - There are new confirmed internal transactions. Being confirmed means that the transactions are verified by miners and added to the next block. 
• New confirmed internal transactions and each confirmation - There are new confirmed internal transactions. Includes also a response at each confirmation the transaction receives until the specified confirmations limit is reached.   
  

With Crypto APIs businesses can make use of useful endpoints to manage their webhooks for Blockchain Events. For example, 

List Blockchain Events Subscriptions: Obtain a list of your callback subscriptions for the available Blockchain Events. 

Get Blockchain Event Subscription Details By Reference ID: Get detailed information for a callback subscription by providing its reference ID. 

Activate Blockchain Event Subscription: Reactivate an event subscription (callback) which has been deactivated by the system. Deactivations could happen due to various reasons, most often "maximum retry attempts reached". 

Delete Blockchain Event Subscription: Through this endpoint the customer can delete blockchain event subscriptions they have previously signed up for. 

Our webhooks for Blockchain Events allow businesses to bring real-time decentralized data to centralized apps. With Crypto APIs users don’t have to constantly poll or run a server 24/7, saving precious time and money while staying ahead in a competitive market. 

To find out more about Blockchain Events or any other of our blockchain products, contact the Crypto APIs team today.