🐳 Crypto Whale-Watching:Build a Real-Time Alert Bot with Blockscout

Get instant alerts on Discord, Slack and more the moment a large transfer happens onchain using Blockscout Pro API websockets.

Andrew G

• 3 min read
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🐳 Crypto Whale-Watching:Build a Real-Time Alert Bot with Blockscout

Whale watching, tracking large wallets and getting notified the moment they move, is a common crypto pastime. Traders and blockchain users monitor whale wallets to get alpha, copy-trade, or identify possible hacks. Whale Alert, the best-known example, flags multi-million-dollar transfers across major chains and tells you whether coins are headed to an exchange (usually a sell signal) or leaving an exchange (often accumulation). Services like Cryptocurrency Alerting go further, letting anyone monitor a whole network with custom rules and push matches out over webhooks, Slack, Discord, or Telegram.

You can build your own version of this in under an hour, for free, using Blockscout's real-time WebSocket API.

Why real-time updates beat polling for whale alerts

The naive approach is a script that polls an address's transaction history every few seconds. It works, but it's slow and wasteful:

  • Your poll interval is your alert delay. Poll every 10 seconds and your fastest possible alert is 10 seconds late. On a fast chain, that's enough time for informed traders to already act on the move before you know about it.
  • Almost every poll finds nothing. You pay in API credits and rate-limit headroom for the 99% of checks that turn up empty, just to catch the 1% that matters.

A push-based connection flips this: subscribe once, and get an event the instant something happens, no wasted requests in between.

Blockscout's real-time layer: the WebSocket API

Blockscout's Pro API gives you a multiplexed WebSocket connection: subscribe to a topic, like a specific address, and the server pushes JSON events to you as they happen. You can turn that stream into an outbound webhook, so it lands directly in Discord, Slack, or anywhere else you'd like

  • Any address, on any of the 100+ chains Blockscout indexes. Point it at an exchange hot wallet, a bridge contract, or a known whale, on Robinhood Chain, Ethereum, or wherever the activity you care about actually happens.
  • Every transfer type in one subscription. Native coin transfers and ERC-20, ERC-721, and ERC-1155 token transfers all flow through the same address subscription, no separate integrations per asset type.
  • Room to scale. A single connection supports up to 100 subscriptions, so tracking ten, or a hundred, known wallets doesn't mean juggling a hundred connections.
  • Built-in resilience. Automatic reconnect with backoff keeps a long-running bot alive through the occasional dropped connection.
  • A free tier to start on. 100,000 API credits a day, enough to run a real alert bot at no cost while you build it out.

For chains like Robinhood Chain, this opens up a genuinely new kind of signal too: Robinhood is bringing tokenized stocks, ETPs, and RWAs onchain, so "whale watching" there isn't just ETH moving between wallets, it can mean tracking large transfers of tokenized equities in real time.

What an alert looks like

Once it's running, a match posts straight to wherever you've pointed it:

🐋 Whale move detected (IN)
0.002 ETH
Tx: https://robinhoodchain.blockscout.com/tx/0x...

Build yours

The full step-by-step guide, complete with copy-paste setup, working code, and configuration for tracking multiple wallets at once, is available in our docs.

docs.blockscout.com/whale-watch →

It walks through getting a free Pro API key, wiring up a Discord webhook, and writing the relay script that connects the two, so you can go from zero to your first live alert in well under an hour.

Get started

FAQ

What is whale watching in crypto?
Whale watching is the practice of monitoring large cryptocurrency wallets and getting notified when they move funds, used as a signal for potential market impact.

How do I get alerted about large crypto transfers in real time?
Subscribe to an address using a real-time data feed like Blockscout's WebSocket API, then forward matching events to a webhook, Discord, Slack, or another destination of your choice.

Does Blockscout support webhooks?
Blockscout's Pro API provides a WebSocket API for real-time blockchain events. You can turn that into a webhook by writing a small relay that forwards matching events to any HTTP endpoint, exactly what this guide walks through.

Can I monitor multiple wallets at once?
Yes. A single Blockscout WebSocket connection supports up to 100 subscriptions, so you can track many addresses, across many chains, without opening multiple connections.