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Bitcoin Beginner 10 min read

mempool.space API for Bitcoin Agents

Query Bitcoin address balances, fee estimates, transaction status, and mempool state with the mempool.space REST API. Endpoint guide with working curl examples.

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"
}