Definition
Core Lightning (CLN), formerly known as c-lightning, is an implementation of a full Lightning Network node maintained by Blockstream under the ElementsProject organization. Written primarily in C, it has run on Bitcoin mainnet since 2018 and emphasizes strict adherence to the Lightning specification (the BOLTs) alongside a small, modular core.
The plugin architecture
The defining trait of CLN is that much of its functionality lives in plugins rather than a monolithic binary. The daemon ships with a JSON-RPC interface, and developers can extend it with plugins written in Python, Rust, Go, or any language that can speak the plugin protocol. This lets node operators add features — custom routing logic, bookkeeping, liquidity automation — without forking the core software, which suits self-hosters who want a lean base they can shape to their own needs.
Running a CLN node
CLN requires a locally running Bitcoin backend, typically Bitcoin Core, to validate the chain and broadcast transactions. It supports mainnet, testnet, signet, and regtest, and is packaged in several sovereignty-focused node distributions. Its Rust crate and language bindings have made it a popular base for builders who want fine-grained control.
CLN is one of several spec-compliant node implementations, each with its own language and design philosophy; we describe them neutrally so operators can pick what fits. For context on the alternatives, see our entries on LND (Lightning Network Daemon) and Eclair.
In Simple Terms
Core Lightning (CLN), formerly known as c-lightning, is an implementation of a full Lightning Network node maintained by Blockstream under the ElementsProject organization. Written primarily…