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In a nutshell
Webhooks push real-time notifications to your server when events occur—deposits, withdrawals, swaps, and more. Instead of polling the API, your server receives instant updates as transactions complete.

Prerequisites

Before setting up webhooks, ensure you have:
1

API Key

Get your API key from the Blockradar Dashboard. Navigate to Developers to generate one.
2

Webhook Endpoint

Create a POST endpoint on your server that can receive JSON payloads and return a 200 OK response.
3

HTTPS URL (Production)

For production, your webhook URL must use HTTPS. For local testing, use tools like ngrok or webhook.site.
4

Master Wallet

Configure your webhook URL on your master wallet via the dashboard.

How It Works

When you make a request to an API endpoint, you expect to get a near-immediate response. However, some requests may take a long time to process, which can lead to timeout errors. In order to prevent a timeout error, a pending response is returned. Since your records need to be updated with the final state of the request, you need to either:
  1. Make a request for an update (popularly known as polling) or,
  2. Listen to events by using a webhook URL.
Helpful Tip
We recommend that you use webhook to provide value to your customers over using callbacks or polling. With callbacks, we don’t have control over what happens on the customer’s end. Neither do you. Callbacks can fail if the network connection on a customer’s device fails or is weak or if the device goes off after a transaction.

Polling vs Webhooks

Polling requires making a GET request at regular intervals to get the final status of a request. For example, when you issue an address to a customer for deposits, you keep making a request for transactions linked to the address until you find one. With webhooks, the resource server, Blockradar in this case, sends updates to your server when the status of your request changes. The change in status of a request is known as an event. You’ll typically listen to these events on a POST endpoint called your webhook URL. The table below highlights some differences between polling and webhooks:

Create a webhook URL

A webhook URL is simply a POST endpoint that a resource server sends updates to. The URL needs to parse a JSON request and return a 200 OK:
When your webhook URL receives an event, it needs to parse and acknowledge the event. Acknowledging an event means returning a 200 OK in the HTTP header. Without a 200 OK in the response header, we’ll keep sending events for the next 2 hours and 35 minutes:
  • We’ll attempt to send webhooks 5 times with an increasing delay between each attempt, starting with 5 minutes and increasing exponentially up to 80 minutes. The total duration for these 5 attempts will span approximately 2 hours and 35 minutes.
Avoid long-running tasks
If you have long-running tasks in your webhook function, you should acknowledge the event before executing the long-running tasks. Long-running tasks will lead to a request timeout and an automatic error response from your server. Without a 200 OK response, we retry as described in the paragraph above.

Testing Webhooks Locally

During development, you can configure your webhook URL in your TEST master wallet environment to a local address, such as http://localhost or 127.0.0.1. To expose your local server to the internet for testing purposes, consider using a tool like ngrok or webhook.site. These tools allow you to see what the webhook payload looks like and simulate webhook events locally before deploying your application to a live environment. Using these tools, you can ensure that your webhook integration is functioning correctly and handle any issues in a controlled, local environment before moving to production.

Resend Transaction Webhook

Incase where for some reasons you don’t receive transaction webhook and the backoff time is elapse, we’ve provided an API you can use to resend a transaction webhook
Use with caution!
As this can lead to processing already completed transactions, make sure you have proper validation in place while using this endpoint.

Verify event origin

Since your webhook URL is publicly available, you need to verify that events originate from Blockradar and not a bad actor. There are two ways to ensure events to your webhook URL are from Blockradar:
  1. Signature validation (recommended)

Signature validation

Events sent from Blockradar carry the x-blockradar-signature header. The value of this header is a HMAC SHA512 signature of the event payload signed using your secret key. Verifying the header signature should be done before processing the event:

Go Live Checklist

Now that you’ve successfully created your webhook URL, here are some ways to ensure you get a delightful experience:
  • Add the webhook URL on your Master wallets on the Blockradar dashboard
  • Ensure your webhook URL is publicly available (localhost URLs cannot receive events)
  • If using .htaccess, kindly remember to add the trailing / to the URL
  • Test your webhook to ensure you’re getting the JSON body and returning a 200 OK HTTP response
  • If your webhook function has long-running tasks, you should first acknowledge receiving the webhook by returning a 200 OK before proceeding with the long-running tasks
  • If we don’t get a 200 OK HTTP response from your webhooks, we flag it as a failed attempt
  • We’ll attempt to send webhooks 5 times with an increasing delay between each attempt, starting with 5 minutes and increasing exponentially up to 80 minutes. The total duration for these 5 attempts will span approximately 2 hours and 35 minutes.

Types of events

Here are the events we currently raise. We would add more to this list as we hook into more actions in the future.

Event Examples

Below are examples of webhook payloads for some of the most common events:

Complete Event List

Transaction Types and Statuses

Transaction Types

The following transaction types are used in webhook payloads:

Transaction Statuses

The following statuses indicate the current state of a transaction:
These transaction types and statuses are used in the type and status fields of webhook payloads to help you understand what kind of transaction occurred and its current state.
Happy hacking! ❤️