Mempool.space API

Open-source Bitcoin mempool and blockchain explorer API with fee estimates, block data, and transaction tracking.

Status
🟢 Online · 737 ms

30-day uptime
90.19%

Free tier
Unlimited, no key, no credit card

Auth
No key required

Last 30 days

Free alternatives (live ranking)

Kraken Public API — 🟢 Online · Unlimited public data, no key required
Coinbase Advanced Trade API (Public) — 🟢 Online · 10 calls/sec, no key for public endpoints
Blockchain.com Data API — 🟢 Online · Unlimited, no key, no credit card

Compare Mempool.space API with…

Mempool.space API vs Kraken Public API — Unlimited public data, no key required
Mempool.space API vs Coinbase Advanced Trade API (Public) — 10 calls/sec, no key for public endpoints
Mempool.space API vs Blockchain.com Data API — Unlimited, no key, no credit card

Official docs ↗

Frequently Asked Questions

Does Mempool.space API require an API key?

No, Mempool.space API is freely accessible without registration or an API key.

What is Mempool.space API's free tier?

Unlimited, no key, no credit card

Is Mempool.space API currently online?

We check Mempool.space API every hour. The current status is shown at the top of this page. You can also see the 30-day uptime history in the chart above.

Implementation notes

When to use Mempool.space API

Mempool.space is the authoritative free API for Bitcoin fee estimation, mempool state, and block data. If you are building a Bitcoin wallet, fee calculator, or block explorer, this is the primary source — it reflects the actual state of Bitcoin's decentralised mempool directly.

Common pitfalls

The `recommended` fee endpoint (`/api/v1/fees/recommended`) returns fee rates in sat/vB. The `fastestFee` is for sub-10-minute confirmation, `halfHourFee` for ~30 minutes, and `hourFee` for ~1 hour. These are estimates based on current mempool state and can change rapidly during block congestion.
Mempool.space offers both a public hosted API and a self-hostable instance. The public API at `mempool.space` is rate-limited for high-volume use; the documentation recommends running your own instance for production wallet backends.
Transaction data endpoints return segwit-native format by default. Legacy address formats (P2PKH, P2SH) are supported but require careful handling of the `vin` and `vout` format differences.
The WebSocket API (`wss://mempool.space/api/v1/ws`) provides real-time updates for new blocks and transactions but requires specific subscription messages after connecting. The REST API and WebSocket API are documented separately.

Quick start (bash)

curl "https://mempool.space/api/v1/fees/recommended"

From our monitoring

Mempool.space is consistently fast and available in our monitoring, with response times typically under 200ms. As an open-source project with broad community support, it has maintained excellent uptime.

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