mempool.space API
Free, no-key Bitcoin mempool + fee-estimation API powering the popular mempool.space explorer; ideal for fee bumping and confirmation tracking.
mempool.space exposes a free public REST API (an Esplora-compatible superset) with no API key required. Beyond standard block/tx/address reads it adds rich mempool intelligence: recommended fee rates by priority, projected mempool blocks, mining pool stats, and Lightning Network data. The recommended-fees endpoint is the most-used: it returns fastest/halfHour/hour/economy/minimum sat/vB tiers in a single call, which is exactly what an automation needs to set or bump a Bitcoin fee. Testnet and Signet instances exist under /testnet and /signet path prefixes. Verified live June 2026.
Free tier
Free public API. A paid Mempool Enterprise offering exists for dedicated/SLA access, but the public endpoints are free.Rate limits
Not published as exact numbers, but the docs state that exceeding limits returns HTTP 429, and repeatedly exceeding them can get your IP banned. Use Enterprise or self-host for heavy/automated workloads.Auth
No keyBase URL
https://mempool.space/apiWhat you'd build with it
- Set or bump Bitcoin transaction fees programmatically
- Monitor mempool congestion to time a broadcast
- Track confirmation status of a pending transaction
- Pull Lightning Network stats for a dashboard
Key endpoints
- GET
/v1/fees/recommendedRecommended fee rates (fastest/halfHour/hour/economy/minimum) in sat/vB - GET
/v1/fees/mempool-blocksProjected mempool blocks with fee ranges and sizes - GET
/mempoolCurrent mempool backlog stats (count, vsize, total fees) - GET
/blocks/tip/heightCurrent best block height - GET
/address/:addressAddress chain + mempool stats (Esplora-compatible) - GET
/v1/lightning/statistics/latestLatest Lightning Network aggregate statistics
Members get the runnable recipe
Sign in free to copy the example request, see a sample response, and read the gotchas.