FastPath API — Bitcoin RPC + Identity

⚡ Quick Start

Get a key, make a request. That's it.

1. Get Your API Key

Send Lightning payment to [email protected], then email [email protected] with payment hash. Keys issued within 1 hour.

2. Make Your First Call

# Get current Bitcoin block height
curl https://api.nativebtc.org/v1/block-height \
  -H "X-API-Key: fp_your_key_here"

# JSON-RPC — works with ethers.js, web3.js, viem
curl -X POST https://api.nativebtc.org/v1/rpc \
  -H "Content-Type: application/json" \
  -H "X-API-Key: fp_your_key_here" \
  -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

3. Use with ethers.js

const { JsonRpcProvider } = require('ethers');

const provider = new JsonRpcProvider(
  'https://api.nativebtc.org/v1/rpc',
  { name: 'bitcoin', chainId: 0xD9B4BEF9 },
  { staticNetwork: true, batchMaxCount: 1,
    fetchOptions: { headers: { 'X-API-Key': 'fp_your_key_here' } } }
);

const block = await provider.getBlockNumber();
console.log('Bitcoin block:', block);

📡 Endpoints

Method	Path	Description
POST	/v1/rpc	JSON-RPC — `eth_*` translated to Bitcoin + native BTC methods
GET	/v1/block-height	Current Bitcoin block height
GET	/v1/fee-estimate?blocks=6	Fee estimate (sat/vB) for target confirmation
GET	/v1/balance/:address	Address balance (Bitcoin or EVM-translated)
GET	/v1/utxos/:address	UTXO set for a Bitcoin address
GET	/v1/tx/:txid	Transaction details by txid
GET	/v1/identity/evm-to-btc/:address	Resolve EVM address → BTC identity
GET	/v1/identity/btc-to-evm/:address	Resolve BTC address → EVM identity
GET	/v1/derive/:chain/:evmAddress	Derive chain address (solana, xrp, cardano, polkadot, tron)
GET	/v1/tiers	Available API tiers no auth
GET	/health	Service health check no auth

🧠 Mempool Intelligence new

Method	Path	Description
GET	/v1/mempool/stats	Mempool size, fees, congestion level, fee estimates for 1–144 blocks
GET	/v1/mempool/fees?target=10	Fee landscape — distribution histogram + recommended rate for target
GET	/v1/mempool/txs?limit=25&sort=fee_desc	Paginated mempool snapshot (sort: fee_desc, time_desc, size_desc)
GET	/v1/mempool/address/:address	Pending transactions for a Bitcoin address
GET	/v1/mempool/tx/:txid	Detailed mempool entry — fees, ancestors, descendants, RBF flag
GET	/v1/mempool/tx/:txid/replacements	RBF replacement tracking — was this tx bumped?
WS	/v1/mempool/stream?key=fp_xxx	WebSocket — live stream of new mempool transactions + stats

🔌 Supported RPC Methods

All standard Ethereum JSON-RPC methods are translated to Bitcoin equivalents in real-time.

EVM Method	Bitcoin Equivalent	Notes
eth_chainId	—	Returns `0xD9B4BEF9` (Bitcoin mainnet magic)
eth_blockNumber	getblockcount	Current block height
eth_getBalance	UTXO scan	Address balance in satoshis
eth_gasPrice	estimatesmartfee	Fee rate in sat/vB
eth_getBlockByNumber	getblock	Full block data
eth_getTransactionByHash	getrawtransaction	Decoded transaction
eth_sendRawTransaction	sendrawtransaction	Broadcast signed tx

Native Bitcoin RPC methods (getblock, estimatesmartfee, etc.) are also supported directly.

🧠 Mempool Intelligence

Real-time mempool data direct from our Bitcoin Core full node. Fee sniping, RBF tracking, congestion monitoring.

Fee Landscape

# Get fee distribution + recommended rate for 6-block target
curl "https://api.nativebtc.org/v1/mempool/fees?target=6" \
  -H "X-API-Key: fp_your_key_here"

# Response includes histogram of fee rates across entire mempool

Live Mempool Stream (WebSocket)

const ws = new WebSocket(
  'wss://api.nativebtc.org/v1/mempool/stream?key=fp_your_key_here'
);

ws.onmessage = (event) => {
  const msg = JSON.parse(event.data);

  if (msg.type === 'new_txs') {
    console.log(`${msg.count} new txs`, msg.transactions);
  }

  if (msg.type === 'stats') {
    console.log('Mempool:', msg.data.mempool.size, 'txs');
  }
};

// Commands: subscribe:txs, subscribe:stats, filter:address:bc1q...
ws.send('subscribe:stats');

Track Address for Incoming Payments

# See pending transactions for any Bitcoin address
curl "https://api.nativebtc.org/v1/mempool/address/bc1q..." \
  -H "X-API-Key: fp_your_key_here"

# Returns direction (incoming/outgoing), fee rate, value

RBF Replacement Detection

# Check if a transaction was replaced (fee bumped)
curl "https://api.nativebtc.org/v1/mempool/tx/abc123.../replacements" \
  -H "X-API-Key: fp_your_key_here"

# Returns: wasReplaced, replacedBy txid, fee delta

💰 Pricing

⚡ Lightning Payments LIVE!

Pay in Bitcoin. Get your API key within 1 hour.
No credit cards. No banks. Bitcoin-native.

Send Lightning payment to:

⚡ [email protected]

After payment, email [email protected] with:
1. Payment hash or screenshot
2. Your project name
3. Tier you paid for

Micro

1,000 sats

~$1 USD

100 API calls

Try it out

Starter

10,000 sats

~$10 USD

1,000 API calls

All endpoints

Small projects

Pro popular

50,000 sats

~$50 USD

5,000 API calls

Priority support

Production apps

Custom

You negotiate

Whatever you need

Dedicated resources

High volume

💳 Payment Options

⚡ Lightning — [email protected] (instant!)

₿ On-chain — Available for custom tiers (email us)

💳 Credit Card — Coming soon

🔑 Authentication

Pass your API key via the X-API-Key header on every request:

curl https://api.nativebtc.org/v1/block-height \
  -H "X-API-Key: fp_your_key_here"

Rate limit info is returned in response headers: X-RateLimit-Limit, X-RateLimit-Remaining, X-DailyLimit-Remaining.

If you exceed your limit, you'll receive a 429 with a Retry-After header.

🚀 Ready to Build?

Send sats via Lightning. Get your API key within 1 hour.

⚡ [email protected]

Email Payment Confirmation →

Bitcoin-only. No credit cards. No banks.

₿ FastPath API