Using a pruned Bitcoin Core node

Core Lightning requires JSON-RPC access to a fully synchronized bitcoind in order to synchronize with the Bitcoin network.

Access to ZeroMQ is not required and bitcoind does not need to be run with txindex like other implementations.

The lightning daemon will poll bitcoind for new blocks that it hasn't processed yet, thus synchronizing itself with bitcoind.

If bitcoind prunes a block that Core Lightning has not processed yet, e.g., Core Lightning was not running for a prolonged period, then bitcoind will not be able to serve the missing blocks, hence Core Lightning will not be able to synchronize anymore and will be stuck.

In order to avoid this situation you should be monitoring the gap between Core Lightning's blockheight using [lightning-cli](ref:lightning-cli) getinfo and bitcoind's blockheight using bitcoin-cli getblockchaininfo. If the two blockheights drift apart it might be necessary to intervene.

Connecting to Bitcoin Core remotely

You can use trusted third-party plugins as bitcoin backends instead of using your own node.

• sauron is a bitcoin backend plugin relying on Esplora.
• trustedcoin is a plugin that uses block explorers (blockstream.info, mempool.space, blockchair.com and blockchain.info) as backends instead of your own bitcoin node.
• bps is a proxy server that exposes just the RPC commands that lightning needs. There's a public endpoint at https://coinos.io/proxy or you can host your own.