Bitcoin Core RPC

The Bitcoin Core RPC is the JSON-RPC interface that a Bitcoin Core node exposes for programmatic access; it is on by default in bitcoind, while the GUI needs server=1. Wallets, block explorers, Lightning nodes, Electrum servers, and basically every Bitcoin service runs against an RPC connection to a backing Bitcoin Core node.

Connection basics:

• Default port is 8332 for mainnet, 18332 for testnet, 38332 for signet. Configurable via rpcport in bitcoin.conf.
• Authentication is via either a generated cookie file in the data directory (the default, and the method Bitcoin Core's docs prefer) or an rpcauth line in the config, which stores a salted hash of the password. Username / password in cleartext is supported but discouraged.
• Format is JSON-RPC over HTTP. Since Bitcoin Core 28.0 the server answers in JSON-RPC 2.0 when a request asks for it, and uses the older 1.1-style protocol otherwise. Each call is a single HTTP POST with a method name and parameters.

The standard CLI driver is bitcoin-cli, which wraps RPC in a shell-friendly interface. bitcoin-cli getblockchaininfo is roughly equivalent to curl -X POST -d '{"jsonrpc":"1.0","method":"getblockchaininfo","params":[]}' http://user:pass@localhost:8332/.

The RPC surface is enormous. Categories you'll see in practice:

• Blockchain queries. getblock, getblockhash, getblockchaininfo, getbestblockhash, getrawtransaction.
• Wallet operations. sendtoaddress, getbalance, listunspent, listtransactions, signrawtransactionwithwallet, walletprocesspsbt.
• Mempool inspection. getmempoolinfo, getrawmempool, getmempoolentry.
• Network state. getpeerinfo, getconnectioncount, getnetworkinfo.
• Mining helpers. getblocktemplate, submitblock, getmininginfo.
• Diagnostic. getmemoryinfo, gettxoutsetinfo, validateaddress.

Security: the RPC is by default bound to localhost only. It has no built-in encryption (Bitcoin Core dropped RPC SSL in version 0.12), and Bitcoin Core's docs say not to expose it to the public internet, warning that even a Tor onion service could open it to attacks it was never hardened against. For remote management of a home node, the docs point to a VPN or an SSH tunnel. JSON-RPC over Tor covers the onion setup some operators use anyway. The rpcwhitelist setting (added in Bitcoin Core 0.20) lets operators restrict each authenticated user to a specific subset of methods (a block explorer doesn't need wallet RPC access), but the docs warn not to treat it as a hard security boundary.

For users of Bitcoin-on-top services, the RPC is invisible plumbing. For anyone running infrastructure - exchanges, payment processors, Lightning routing nodes - it's the daily working surface of Bitcoin Core.