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Bitcoin Beginner 10 min read

mempool.space API Reference

Complete API reference for mempool.space Bitcoin explorer. Addresses, transactions, blocks, fees, and mempool data.

api mempool rest

mempool.space API Reference

mempool.space provides a free, open-source Bitcoin explorer API. It’s the recommended API for agents due to its reliability, comprehensive data, and no authentication requirements.

Base URLs

NetworkURL
Mainnethttps://mempool.space/api
Testnethttps://mempool.space/testnet/api
Signethttps://mempool.space/signet/api

Rate Limits

  • No API key required
  • ~10 requests/second (soft limit)
  • Consider running your own instance for high volume

Address Endpoints

Get Address Info

GET /address/{address}

Response:

{
  "address": "bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq",
  "chain_stats": {
    "funded_txo_count": 10,
    "funded_txo_sum": 500000,
    "spent_txo_count": 5,
    "spent_txo_sum": 300000,
    "tx_count": 15
  },
  "mempool_stats": {
    "funded_txo_count": 0,
    "funded_txo_sum": 0,
    "spent_txo_count": 0,
    "spent_txo_sum": 0,
    "tx_count": 0
  }
}

Get Address UTXOs

GET /address/{address}/utxo

Response:

[
  {
    "txid": "abc123...",
    "vout": 0,
    "status": {
      "confirmed": true,
      "block_height": 830000,
      "block_hash": "000000000...",
      "block_time": 1706745600
    },
    "value": 100000
  }
]

Get Address Transactions

GET /address/{address}/txs

Returns up to 25 most recent transactions.

Pagination:

GET /address/{address}/txs/chain/{last_seen_txid}

Transaction Endpoints

Get Transaction

GET /tx/{txid}

Response:

{
  "txid": "abc123...",
  "version": 2,
  "locktime": 0,
  "vin": [{
    "txid": "prev123...",
    "vout": 0,
    "prevout": {
      "scriptpubkey": "0014...",
      "scriptpubkey_address": "bc1q...",
      "scriptpubkey_type": "v0_p2wpkh",
      "value": 100000
    },
    "scriptsig": "",
    "witness": ["304402...", "02a1b2..."],
    "is_coinbase": false,
    "sequence": 4294967293
  }],
  "vout": [{
    "scriptpubkey": "0014...",
    "scriptpubkey_address": "bc1q...",
    "scriptpubkey_type": "v0_p2wpkh",
    "value": 50000
  }],
  "size": 222,
  "weight": 561,
  "fee": 1000,
  "status": {
    "confirmed": true,
    "block_height": 830000,
    "block_hash": "000000000...",
    "block_time": 1706745600
  }
}

Get Transaction Status

GET /tx/{txid}/status

Response:

{
  "confirmed": true,
  "block_height": 830000,
  "block_hash": "000000000...",
  "block_time": 1706745600
}

Get Raw Transaction

GET /tx/{txid}/hex

Returns raw transaction hex string.

Broadcast Transaction

POST /tx
Content-Type: text/plain

{raw_tx_hex}

Success Response: Returns txid Error Response:

{
  "error": "bad-txns-inputs-missingorspent"
}

Block Endpoints

Get Block

GET /block/{hash}

Get Block Height

GET /block-height/{height}

Returns block hash at given height.

Get Block Transactions

GET /block/{hash}/txs
GET /block/{hash}/txs/{start_index}

Returns 25 transactions per page.

Get Latest Block Height

GET /blocks/tip/height

Returns current blockchain height as integer.

Get Latest Block Hash

GET /blocks/tip/hash

Fee Endpoints

GET /v1/fees/recommended

Response:

{
  "fastestFee": 45,
  "halfHourFee": 35,
  "hourFee": 25,
  "economyFee": 15,
  "minimumFee": 8
}

Fee Histogram

GET /v1/fees/mempool-blocks

Response:

[
  {
    "blockSize": 1500000,
    "blockVSize": 1000000,
    "nTx": 2500,
    "totalFees": 25000000,
    "medianFee": 25,
    "feeRange": [15, 20, 25, 30, 45, 100]
  }
]

Mempool Endpoints

Mempool Stats

GET /mempool

Response:

{
  "count": 45000,
  "vsize": 85000000,
  "total_fee": 12500000000,
  "fee_histogram": [
    [25, 1500000],
    [20, 3000000],
    [15, 5000000]
  ]
}

Recent Mempool Transactions

GET /mempool/recent

Returns 10 most recent mempool entries.

Price Endpoints

Current Price

GET /v1/prices

Response:

{
  "USD": 97500,
  "EUR": 89000,
  "GBP": 77000,
  "time": 1706745600
}

Historical Price

GET /v1/historical-price?currency=USD&timestamp={unix_timestamp}

WebSocket API

Real-time updates via WebSocket:

wss://mempool.space/api/v1/ws

Subscribe to Address

{"track-address": "bc1q..."}

Subscribe to Mempool

{"track-mempool": true}

Subscribe to Blocks

{"track-blocks": true}

Agent Code Examples

Check Address Balance

import requests

def get_balance(address):
    url = f"https://mempool.space/api/address/{address}"
    response = requests.get(url)
    data = response.json()

    confirmed = data['chain_stats']['funded_txo_sum'] - data['chain_stats']['spent_txo_sum']
    unconfirmed = data['mempool_stats']['funded_txo_sum'] - data['mempool_stats']['spent_txo_sum']

    return {
        'confirmed': confirmed,
        'unconfirmed': unconfirmed,
        'total': confirmed + unconfirmed
    }

Wait for Confirmation

import time

def wait_for_confirmation(txid, target_confirmations=1, timeout=3600):
    start = time.time()

    while time.time() - start < timeout:
        response = requests.get(f"https://mempool.space/api/tx/{txid}/status")
        status = response.json()

        if status.get('confirmed'):
            tip = requests.get("https://mempool.space/api/blocks/tip/height").text
            confirmations = int(tip) - status['block_height'] + 1

            if confirmations >= target_confirmations:
                return {
                    'confirmed': True,
                    'confirmations': confirmations,
                    'block_height': status['block_height']
                }

        time.sleep(30)  # Check every 30 seconds

    return {'confirmed': False, 'timeout': True}

Broadcast Transaction

def broadcast_tx(tx_hex):
    response = requests.post(
        "https://mempool.space/api/tx",
        data=tx_hex,
        headers={'Content-Type': 'text/plain'}
    )

    if response.status_code == 200:
        return {'success': True, 'txid': response.text}
    else:
        return {'success': False, 'error': response.text}

Get Optimal Fee

def get_fee_rate(priority='normal'):
    response = requests.get("https://mempool.space/api/v1/fees/recommended")
    fees = response.json()

    priority_map = {
        'urgent': 'fastestFee',
        'normal': 'halfHourFee',
        'economy': 'economyFee',
        'minimum': 'minimumFee'
    }

    key = priority_map.get(priority, 'halfHourFee')
    return fees[key]

Self-Hosting

For high-volume agents, run your own mempool.space instance:

git clone https://github.com/mempool/mempool
cd mempool
docker-compose up -d

Requires Bitcoin Core with txindex=1.

Machine-Readable Summary

{
  "topic": "mempool-space-api",
  "base_url": "https://mempool.space/api",
  "authentication": "none",
  "rate_limit": "~10/second",
  "endpoints": {
    "address": "/address/{address}",
    "utxos": "/address/{address}/utxo",
    "transaction": "/tx/{txid}",
    "broadcast": "POST /tx",
    "fees": "/v1/fees/recommended",
    "mempool": "/mempool",
    "price": "/v1/prices"
  },
  "websocket": "wss://mempool.space/api/v1/ws"
}