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What is Eclair?

A plain-language explainer of Eclair, the Lightning Network, and how the two fit together.

Eclair is a Lightning Network node implementation written in the Scala programming language and maintained by ACINQ. A “node implementation” is the software that operates a Lightning node: it opens and manages payment channels, forwards (routes) payments across the network, and speaks the same protocol as every other Lightning node. Eclair runs on the Java Virtual Machine (JVM), relies on a Bitcoin Core full node for its view of the blockchain, and is released under the Apache 2.0 open-source license.

The Lightning Network in one paragraph

Bitcoin’s base layer settles transactions on-chain, which is secure but limited in throughput and not ideal for small, frequent payments. The Lightning Network is a “layer 2” protocol built on top of Bitcoin: two parties lock funds into a payment channel and can then exchange near-instant, low-fee payments off-chain, settling to the blockchain only when they close the channel. Channels link together into a network, so a payment can hop across several nodes to reach someone you don’t have a direct channel with. Eclair is one of the programs that can run such a node.

Where Eclair fits

There are several independent Lightning implementations, each written in a different language and aimed at slightly different users. Eclair’s niche is server-side, high-reliability routing nodes. It ships as a headless daemon controlled through an API rather than a consumer wallet with a graphical interface, which makes it a natural fit for exchanges, payment processors, and operators running large nodes.

What Eclair is

A full, BOLT-compliant Lightning node
A headless daemon you run on a server
Controlled via JSON-RPC API and eclair-cli
Backed by a Bitcoin Core node

What Eclair is not

Not a desktop or mobile wallet with a GUI
Not a custodial service
Not a replacement for a Bitcoin full node
Not affiliated with this website

Who builds it

Eclair is developed by ACINQ, a company that has been a long-standing contributor to the Lightning protocol and the BOLT specifications. ACINQ also builds the Phoenix wallet, and Eclair is the node technology behind much of ACINQ’s own Lightning infrastructure. Because Eclair is open source, anyone can read the code, run it, and contribute on GitHub.

How Eclair is put together

At a high level, Eclair sits between the peer-to-peer Lightning network and your Bitcoin node:

  Lightning peers  ⇄  Eclair (JVM daemon)  ⇄  Bitcoin Core (bitcoind)
                          │
                          ├─ JSON-RPC API
                          └─ eclair-cli / plugins

Eclair watches the blockchain through Bitcoin Core, maintains channel state, gossips with other nodes to learn the network graph, and finds routes for outgoing payments. You interact with it through its API — there’s no built-in GUI.

Explore the features Install Eclair