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Qtum Eclair is a scala implementation of the Lightning Network. It can run with or without a GUI, and a JSON-RPC API is also available. Qtum Eclair is a fork of Eclair to be compatible with Qtum.

This software follows the Qtum Lightning Network Specifications. Other implementations include qtum-lightning.

🚧 Both the BOLTs and Qtum Eclair itself are still a work in progress. Expect things to break/change!

🚨 If you intend to run Qtum Eclair on mainnet:

  • Keep in mind that it is beta-quality software and don't put too much money in it
  • Qtum Eclair's JSON-RPC API should NOT be accessible from the outside world (similarly to QTUM Core API)
  • Specific configuration instructions for mainnet are provided below

Lightning Network Specification Compliance

Please see the latest release note for detailed information on BOLT compliance.


Eclair Demo


Eclair offers a feature rich HTTP API that enables application developers to easily integrate.

For more information please visit the API documentation website.

⚠️ You can still use the old API by setting the eclair.api.use-old-api=true parameter, but it is now deprecated and will soon be removed. The old documentation is still available here.


Configuring QTUM Core

⚠️ Qtum Eclair requires QTUM Core 0.17.0 or higher. If you are upgrading an existing wallet, you need to create a new address and send all your funds to that address.

Qtum Eclair needs a synchronized, segwit-ready, zeromq-enabled, wallet-enabled, non-pruning, tx-indexing Qtum Core node. Qtum Eclair will use any QTUM it finds in the QTUM Core wallet to fund any channels you choose to open. Qtum Eclair will return QTUM from closed channels to this wallet.

Run qtumd with the following minimal qtum.conf:


Installing Qtum Eclair

Qtum Eclair is developed in Scala, a powerful functional language that runs on the JVM, and is packaged as a JAR (Java Archive) file. We provide 2 different packages, which internally use the same core libraries:

  • eclair-node, which is a headless application that you can run on servers and desktops, and control from the command line
  • eclair-node-gui, which also includes a JavaFX GUI

To run Qtum Eclair, you first need to install Java, we recommend that you use OpenJDK 11. Qtum Eclair will also run on Oracle JDK 1.8, Oracle JDK 11, and other versions of OpenJDK but we don't recommend using them.

Then download the latest fat jar and depending on whether or not you want a GUI run the following command:

  • with GUI:
java -jar eclair-node-gui-<version>-<commit_id>.jar
  • without GUI:
java -jar eclair-node-<version>-<commit_id>.jar

Configuring Qtum Eclair

Configuration file

Qtum Eclair reads its configuration file, and write its logs, to ~/.qtum-eclair by default.

To change your node's configuration, create a file named eclair.conf in ~/.qtum-eclair. Here's an example configuration file:


Here are some of the most common options:

name description default value
eclair.chain Which blockchain to use: regtest, testnet or mainnet mainnet
eclair.server.port Lightning TCP port 9735
eclair.api.enabled Enable/disable the API false. By default the API is disabled. If you want to enable it, you must set a password.
eclair.api.port API HTTP port 8080
eclair.api.password API password (BASIC) "" (must be set if the API is enabled)
eclair.bitcoind.rpcuser Qtum Core RPC user foo
eclair.bitcoind.rpcpassword Qtum Core RPC password bar
eclair.bitcoind.zmqblock Qtum Core ZMQ block address "tcp://"
eclair.bitcoind.zmqtx Qtum Core ZMQ tx address "tcp://"
eclair.gui.unit Unit in which amounts are displayed (possible values: msat, sat, bits, mbtc, btc) btc

Quotes are not required unless the value contains special characters. Full syntax guide here.

→ see reference.conf for full reference. There are many more options!

Java Environment Variables

Some advanced parameters can be changed with java environment variables. Most users won't need this and can skip this section.

⚠️ Using separate datadir is mandatory if you want to run several instances of Qtum Eclair on the same machine. You will also have to change ports in eclair.conf (see above).

name description default value
eclair.datadir Path to the data directory ~/.qtum-eclair
eclair.headless Run eclair without a GUI
eclair.printToConsole Log to stdout (in addition to eclair.log)

For example, to specify a different data directory you would run the following command:

java -Declair.datadir=/tmp/node1 -jar lightning-capsule.jar


Qtum Eclair uses logback for logging. To use a different configuration, and override the internal logback.xml, run:

java -Dlogback.configurationFile=/path/to/logback-custom.xml -jar eclair-node-gui-<version>-<commit_id>.jar


The files that you need to backup are located in your data directory. You must backup:

  • your seed (seed.dat)
  • your channel database (eclair.sqlite.bak under directory mainnet, testnet or regtest depending on which chain you're running on)

Your seed never changes once it has been created, but your channels will change whenever you receive or send payments. Eclair will create and maintain a snapshot of its database, named eclair.sqlite.bak, in your data directory, and update it when needed. This file is always consistent and safe to use even when Eclair is running, and this is what you should backup regularly.

For example you could configure a cron task for your backup job. Or you could configure an optional notification script to be called by eclair once a new database snapshot has been created, using the following option:

eclair.backup-notify-script = "/absolute/path/to/"

Make sure that your script is executable and uses an absolute path name for eclair.sqlite.bak.

Note that depending on your filesystem, in your backup process we recommend first moving eclair.sqlite.bak to some temporary file before copying that file to your final backup location.


cd lightning-demo
docker build -t qtum-eclair-img .

You can use the JAVA_OPTS environment variable to set arguments to eclair-node.

docker run -ti --rm -e "JAVA_OPTS=-Xmx512m -Declair.api.binding-ip= -Declair.node-alias=node-pm -Declair.printToConsole" qtum-eclair-img

If you want to persist the data directory, you can make the volume to your host with the -v argument, as the following example:

docker run -ti --rm -v "/path_on_host:/data" -e "JAVA_OPTS=-Declair.printToConsole" qtum-eclair-img


For advanced usage, Eclair supports plugins written in Scala, Java, or any JVM-compatible language.

A valid plugin is a jar that contains an implementation of the Plugin interface.

Here is how to run Eclair with plugins:

java -jar eclair-node-<version>-<commit_id>.jar <plugin1.jar> <plugin2.jar> <...>

Testnet usage

Eclair is configured to run on mainnet by default, but you can still run it on testnet (or regtest): start your Qtum Node in testnet mode (add testnet=1 in qtum.conf or start with -testnet), and change Eclair's chain parameter and Qtum RPC port:


Following are the minimum configuration files you need to use for QTUM Core and Lightning.

You may also want to take advantage of the new configuration sections in qtum.conf to manage parameters that are network specific, so you can easily run your qtum node on both mainnet and testnet. For example you could use:

QTUM Core configuration



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