Bitcoin API Comparison: Blockstream, mempool.space, and More

Bitcoin API Providers Overview

Building on Bitcoin requires reliable API access to blockchain data: transactions, addresses, UTXOs, fee estimates, mempool state, and more. The choice of API provider affects your application's performance, cost, and the depth of data you can query. Some providers offer raw JSON-RPC access to a Bitcoin node, while others provide indexed REST APIs with richer query capabilities like address balance lookups and UTXO set queries that standard bitcoind RPC does not support natively.

The following table compares the major Bitcoin API providers across the dimensions that matter most to developers: endpoint types, rate limits, pricing, and chain support.

Indexed APIs vs JSON-RPC Proxies

The most important architectural distinction among Bitcoin API providers is whether they offer indexed Bitcoin-specific endpoints or simply proxy requests to a standard bitcoind JSON-RPC interface.

Indexed APIs (Blockstream Esplora, mempool.space) maintain their own database of parsed blockchain data. This lets them offer endpoints that bitcoind cannot: address balance lookups, full transaction history for an address, UTXO set queries, and mempool fee distribution statistics. These endpoints are what most application developers actually need when building wallets, explorers, or payment systems.

JSON-RPC proxies (Alchemy, QuickNode without add-ons, GetBlock) forward your requests to a Bitcoin Core node. You get the same methods available in bitcoin-cli: getblock, getrawtransaction, sendrawtransaction, and so on. These are sufficient for broadcasting transactions and querying individual blocks or transactions by hash, but they lack the address-level indexing that most apps require. QuickNode and GetBlock bridge this gap with optional Blockbook add-ons that provide indexed data.

Provider Deep Dive

Blockstream Esplora

Esplora is Blockstream's open-source block explorer and API. The public API at blockstream.info/api/ requires no authentication and provides approximately 30 REST endpoints covering transactions, addresses, UTXOs, blocks, mempool statistics, and fee estimates. Rate limits on the public instance are roughly 50 requests per second based on nginx configuration. Blockstream also offers a managed Explorer API product with 500,000 free requests per month and API key authentication for higher volumes.

Esplora's greatest strength is that you can self-host it. Running your own instance eliminates rate limits and third-party dependencies entirely. The codebase is written in Rust and is well-maintained. The tradeoff: no WebSocket support, so you must poll for new data.

mempool.space

mempool.space offers the richest Bitcoin-specific API of any provider listed here. Beyond standard address, transaction, and block endpoints, it provides mining pool statistics, difficulty adjustment tracking, replace-by-fee event monitoring, mempool visualization data, and Lightning Network statistics (nodes, channels, network capacity). It also offers a transaction accelerator API for fee bumping.

WebSocket support at wss://mempool.space/api/v1/ws enables real-time subscriptions for new blocks, mempool updates, address activity, and RBF events. The public API requires no authentication but enforces undisclosed rate limits (HTTP 429 responses). Enterprise tiers with higher limits require contacting mempool.space directly. Like Esplora, mempool.space is fully open source and self-hostable.

Alchemy

Alchemy added Bitcoin support as a JSON-RPC proxy running bitcoind (version 30.2 as of early 2026). It supports standard Bitcoin Core RPC methods: getblockcount, getrawtransaction, mempool queries, and transaction broadcasting. The free tier includes 30 million compute units per month with a 25 requests-per-second limit. Pay-as-you-go pricing starts at $0.45 per million compute units, with up to 300 requests per second.

Alchemy is a strong choice if you already use their platform for EVM chains and want a single dashboard. However, it only provides raw JSON-RPC: no address balance endpoints, no UTXO queries, no fee estimation beyond what bitcoind offers natively. For Bitcoin-specific indexed data, you will need a supplementary provider.

QuickNode

QuickNode provides Bitcoin JSON-RPC access with an optional Blockbook add-on that adds 10 indexed methods for balance queries, transaction history, and UTXO lookups. This combination gives you both raw node access and the indexed data most applications need. QuickNode also supports WebSocket connections and offers Streams for real-time data ingestion with exactly-once delivery guarantees.

Pricing starts at $49/month for 50 requests per second and 80 million API credits (Build plan). The free tier allows 15 requests per second with 10 million credits. Higher tiers scale to 500 requests per second at $999/month. QuickNode supports Mainnet and Testnet4, and claims 99.99% uptime SLA.

GetBlock

GetBlock offers Bitcoin JSON-RPC access with Blockbook integration for indexed data. It has the most granular public pricing of any provider: Starter ($39/month, 100 req/s, 50M CU), Advanced ($159/month, 300 req/s, 220M CU), Pro ($399/month, 500 req/s, 600M CU), and Enterprise ($799+/month, custom). The free tier is limited to 20 requests per second and 50,000 compute units. Both shared and dedicated node options are available, with the dedicated tier providing full archive node access.

NOWNodes

NOWNodes provides JSON-RPC, REST (via Blockbook), and WebSocket access. Pricing is in EUR: Pro at 20 EUR/month (1M requests), Business at 200 EUR/month (30M requests), and Enterprise at 500 EUR/month (100M requests). The free Start plan is a one-month trial limited to 100,000 requests: it is not a permanent free tier. Paid plans have no predefined rate limits; throughput scales dynamically. NOWNodes advertises a 99.95% uptime SLA.

Pricing Comparison

Cost structures vary significantly across providers. Some charge per request, others use compute unit systems where different RPC methods consume different amounts of credit. The following table compares pricing tiers for a developer making roughly 1 million requests per month.

Note: Compute unit costs vary by method. A simple getblockcount call consumes fewer units than a getrawtransaction with verbose output. Check each provider's documentation for method-level CU pricing.

How to Choose a Bitcoin API Provider

The right provider depends on your application's requirements. Here are the most common scenarios:

Building a wallet or block explorer: choose mempool.space or Blockstream Esplora. Both provide indexed Bitcoin-specific endpoints for address lookups, UTXO queries, and fee estimation without requiring Blockbook add-ons. mempool.space adds WebSocket support and Lightning Network data.

Running a multi-chain application: Alchemy or QuickNode may be the better fit. Both offer EVM and Bitcoin support under a single dashboard, simplifying key management and billing. QuickNode's Blockbook add-on fills the indexed data gap that Alchemy lacks.

Minimizing cost for a side project or prototype: Blockstream Esplora's public API (no auth, no signup) or mempool.space's public API are the fastest paths to working code. Both are free for moderate usage.

Production applications with high throughput: self-hosting Esplora or mempool.space eliminates rate limits entirely. If managed infrastructure is preferred, QuickNode and GetBlock offer the highest paid-tier rate limits (up to 500 req/s) with SLA guarantees.

For developers building on Bitcoin Layer 2 networks like Spark, the choice of base-layer API still matters for monitoring on-chain settlements and managing UTXOs. The Spark SDK handles L2 operations directly, but applications that bridge between layers need reliable access to both L1 and L2 data. See our Bitcoin for developers guide for a broader look at the developer tooling landscape.

Self-Hosting vs Managed APIs

Both Blockstream Esplora and mempool.space are fully open source, meaning you can run your own instance backed by your own Bitcoin node. Self-hosting eliminates rate limits, removes third-party dependencies, and gives you full control over uptime and data freshness. The tradeoff is infrastructure cost: an Esplora instance requires a fully synced Bitcoin Core node plus an Electrs indexer, which needs roughly 1 TB of SSD storage and 16 GB of RAM.

For most startups and prototypes, the managed free tiers are sufficient. For production applications handling thousands of requests per second, self-hosting or a dedicated node plan from QuickNode or GetBlock is worth the investment. Our Bitcoin node software comparison covers the options for running your own infrastructure.

Frequently Asked Questions

What is the best free Bitcoin API?

Blockstream Esplora and mempool.space are the strongest free options. Both are open source, require no API key for public access, and provide indexed Bitcoin-specific endpoints that JSON-RPC proxies do not offer. mempool.space has the edge for real-time applications thanks to WebSocket support and richer data (mempool stats, mining data, Lightning Network info). Esplora is simpler and well-suited for straightforward address and transaction lookups.

Does Alchemy support Bitcoin?

Yes, Alchemy supports Bitcoin as a JSON-RPC proxy to a bitcoind node. You can call standard Bitcoin Core RPC methods like getblock, getrawtransaction, and sendrawtransaction. However, Alchemy does not provide Bitcoin-specific indexed endpoints for address balance lookups, UTXO queries, or fee estimation beyond what bitcoind offers natively. If your application requires those features, you will need Esplora, mempool.space, or a provider with Blockbook integration.

What is the difference between a Bitcoin REST API and JSON-RPC?

JSON-RPC is the native interface of Bitcoin Core (bitcoind). It exposes methods for interacting with the node: submitting transactions, querying blocks by hash, and reading raw mempool data. REST APIs like Esplora and mempool.space run an indexer on top of a full node, parsing and organizing blockchain data into developer-friendly endpoints. REST APIs can answer queries that JSON-RPC cannot, such as "what is the balance of this address?" or "list all UTXOs for this xpub."

Which Bitcoin API supports WebSocket connections?

mempool.space, QuickNode, and NOWNodes all support WebSocket connections for Bitcoin. mempool.space offers the most comprehensive WebSocket API with subscriptions for new blocks, mempool updates, address tracking, and RBF events. QuickNode provides WebSocket access plus its Streams product for real-time data with delivery guarantees. NOWNodes supports WebSocket subscriptions for new blocks and transactions. Blockstream Esplora and Alchemy do not offer WebSocket support for Bitcoin.

Can I get Lightning Network data from a Bitcoin API?

mempool.space is the only provider in this comparison that includes Lightning Network API endpoints. Its Lightning API covers network-wide statistics, node details, channel information, and historical data. Other providers focus on base-layer Bitcoin data only. For Lightning-specific development, you can also run your own Lightning node and use its native gRPC or REST interface. See our Lightning node comparison for details on LND, CLN, and Eclair APIs.

How many requests per second can I make on free tiers?

Rate limits vary: Blockstream Esplora allows roughly 50 req/s on its public API, Alchemy allows 25 req/s, GetBlock allows 20 req/s, and QuickNode and NOWNodes each allow 15 req/s. mempool.space does not publish its rate limits but returns HTTP 429 responses when they are exceeded. For sustained high-throughput needs, self-hosting Esplora or mempool.space removes rate limits entirely.

Should I self-host a Bitcoin API?

Self-hosting makes sense for production applications with high request volumes, strict uptime requirements, or privacy concerns about sharing query patterns with third parties. Both Esplora and mempool.space are open source and well-documented for self-hosting. The main cost is infrastructure: a fully synced Bitcoin node with an indexer requires approximately 1 TB of SSD storage and 16 GB of RAM. For prototypes, testing, and moderate-traffic apps, managed free tiers are more practical.

This tool is for informational purposes only and does not constitute financial advice. API pricing, rate limits, and feature availability change frequently. Always verify current data on each provider's official documentation and pricing page before making architectural decisions.