Applications that need real-time blockchain monitoring can now use Electrum RPC Protocol alongside REST API, giving developers the complete toolkit for building production Bitcoin and Liquid applications with the Blockstream Explorer API.
What the Blockstream Explorer API Does
Every Bitcoin and Liquid application needs access to blockchain data. When a user opens a wallet, checks a transaction status, or queries an address balance, that application is asking: what's happening on the blockchain right now?
The Blockstream Explorer API is the infrastructure layer that answers those questions, indexing the entire Bitcoin and Liquid blockchains and making that data available through a clean, fast API. Whether building a mobile wallet, a trading dashboard, an analytics platform, or an exchange, Explorer API enables applications to access blockchain state without running their own infrastructure.
Running blockchain infrastructure is resource-intensive. A Bitcoin full node requires hundreds of gigabytes of storage and constant maintenance. But application development requires more than just a node. Indexing infrastructure is needed to query addresses efficiently, caching layers for performance, load balancing for reliability, and monitoring systems to ensure uptime. The Blockstream Explorer API handles all of this so developers can focus on building applications instead of managing servers.
Most applications use the REST API. It's straightforward, stateless, and perfect for on-demand queries. But some applications need more than queries. They need real-time notifications when addresses receive payments, instant alerts when transactions confirm, and the ability to monitor thousands of addresses continuously without repeated API calls.
That's where Electrum RPC comes in.
Why Electrum RPC Matters
Electrum RPC is a persistent, stateful protocol designed for real-time blockchain monitoring. Instead of repeatedly asking "has anything changed?", applications subscribe once and get notified automatically when something happens.
Key capabilities:
- Subscribe to addresses to get push notifications when there is a balance change.
- Subscribe to block headers to get push notifications when a new block is found.
- Batch requests for efficient querying.
Address monitoring delivers instant notifications. Subscribe to an address and get push notifications the moment it receives a transaction or a transaction confirms. No polling. No delays. No wasted API calls checking for updates that haven't happened yet.
Persistent connections enable real-time data streams. Applications can maintain long-lived connections that stream blockchain events as they occur. Perfect for dashboards displaying live transaction feeds, exchanges processing deposits in real-time, or custody platforms monitoring cold storage addresses.
Lower latency supports performance-critical applications. Direct protocol access means faster response times for applications where milliseconds matter, like payment processors confirming transactions or trading platforms tracking mempool activity.
Electrum RPC has been powering Bitcoin wallets for over a decade. It is a battle-tested protocol with broad tooling support, and extensive client libraries exist in every major programming language. Developers already familiar with Electrum-based wallet integrations can use the same tools and patterns.
Available Across All Tiers
Electrum RPC is available on the free public Blockstream Explorer (blockstream.info) with rate limits suitable for individual use and prototyping. Applications exceeding free tier limits will need to upgrade to a paid tier for continued access.
What's new: Electrum RPC is now available across all paid Explorer API tiers with production-grade rate limits designed for high-volume applications.
Basic and Advanced tiers include Electrum RPC access that scales with your API call limits. Enterprise tier provides unlimited Electrum RPC connections with dedicated infrastructure, custom rate limits, and priority support. It's built for exchanges, custody providers, and high-volume applications that demand institutional-grade uptime.
Combining RPC and Quick sync for Maximum Performance
Production applications can potentially achieve optimal performance by combining Electrum RPC with QuickSync. The approach would use Electrum RPC for real-time monitoring and instant notifications, while using QuickSync for fast initial wallet synchronization. QuickSync is built on the Waterfalls protocol, an open-source descriptor-based sync protocol developed by Blockstream's Riccardo Casatta.
Waterfalls offers flexible sync modes. Share a descriptor once and receive complete wallet transaction history in a single response, or use UTXO-only sync to retrieve just the unspent outputs. UTXO-only sync is faster when making a transaction since the wallet only needs to know what it has available to spend, not the full history. Waterfalls can also retrieve the last index, returning an address that hasn't been used yet. What used to take hours now takes minutes.
The theoretical workflow: when a wallet first opens, QuickSync retrieves the complete transaction history quickly. Then Electrum RPC takes over, maintaining a persistent connection to deliver instant notifications as new transactions arrive. This combination could deliver both fast initial sync and real-time updates without the overhead of constant polling. QuickSync is available across all subscription tiers with pricing that scales as teams grow, and it's already running in production through LWK (Liquid Wallet Kit), with GDK and BDK integrations in progress.
Real-World Use Cases
Exchanges need to monitor thousands of deposit addresses simultaneously without overwhelming their infrastructure. Instead of polling each address repeatedly, Electrum RPC lets exchanges subscribe once and receive instant notifications when deposits arrive. This reduces API overhead by orders of magnitude while improving user experience with real-time balance updates.
Custody platforms managing cold storage need immediate alerts when funds move unexpectedly. Electrum RPC eliminates the dangerous gap between polling cycles. Security teams know instantly when monitored addresses show activity, not minutes later when the next polling run completes.
Payment processors need to confirm customer payments the moment they hit the blockchain. Polling creates friction in checkout flows with "pending" states and delayed confirmations. Electrum RPC delivers instant payment detection so customers see confirmations immediately, not after waiting for the next polling cycle.
Trading platforms need real-time notifications when specific addresses receive payments or transactions confirm. Polling introduces latency that matters for time-sensitive deposit processing and withdrawal monitoring. Electrum RPC delivers instant notifications for subscribed addresses, eliminating polling delays for critical transaction tracking.
Analytics dashboards need to display live blockchain activity without constant page refreshes or stale data. Polling creates choppy, outdated interfaces. Electrum RPC keeps dashboards synchronized with blockchain state in real-time, showing users Bitcoin as it happens.
Ready to Get Started?
Electrum RPC is available now across all paid Blockstream Explorer API tiers. Getting started is straightforward: create an account through the self-service dashboard, generate API keys, and start building. The dashboard provides real-time usage monitoring, billing management, API key rotation, and access to comprehensive documentation.
Choose Basic, Advanced, or Enterprise based on your application's needs. Monitor API usage in real-time, track costs, and manage multiple API keys across environments, all from the dashboard.
Learn more: blockstream.info/explorer-api
Enterprise enquiries: blockstream.typeform.com/enterpriseAPI
Documentation: github.com/Blockstream/esplora/blob/master/API.md