Connecting to a Network

Tezos is run on several networks, such as Mainnet (the main network) and various test Networks. Some users may also want to run their own networks for various reasons. Networks differ in various ways:

  • they start from their own genesis block;

  • they have different names so that each node can choose the network to connect to;

  • they may run different protocols (or upgrade protocols at different moments);

  • protocols may run with different constants (for instance, test networks move faster);

  • they have different bootstrap peers (nodes that new nodes connect to initially);

  • some networks may change the protocol without going through the regular voting process, via user-activated upgrades or user-activated protocol overrides.

The Octez node can be configured to connect to a given network when it is started. By default, the node connects to Mainnet. To connect to other networks, you can either use one of the Built-In Networks or configure the node to connect to Custom Networks. See also Alias Versus Explicit Configuration for a discussion regarding what happens when you update your node, in each case.

Test Networks

Mainnet is the main Tezos network, but is not appropriate for testing. A number of test networks are available to this end. Test networks usually run with different constants to speed up the chain.

Each test network listed there also indicates a faucet delivering test tokens. Enter the public key hash of any test account on the corresponding website to receive test tokens.

Built-In Networks

The simplest way to select the network to connect to is to use the --network option for selecting a test network when you initialize your node configuration.

For instance, to run on Ghostnet:

octez-node config init --data-dir ~/tezos-ghostnet --network ghostnet
octez-node identity generate --data-dir ~/tezos-ghostnet
octez-node run --data-dir ~/tezos-ghostnet


Once initialized, the node remembers its network settings on subsequent runs and reconnects to the same network every time you run it. If you specify a different network when running the node again, it will refuse to start. In order to switch to a different network you need to either reinitialize it with a different data directory using the --data-dir option or remove everything from the existing data directory, which defaults to ~/.tezos-node (and also initialize again).

The --network option is not case-sensitive and can be used with the following built-in networks:

  • mainnet (this is the default)

  • sandbox

  • ghostnet

If you did not initialize your node configuration, or if your configuration file contains no network field, the node assumes you want to run Mainnet. You can use the --network option with octez-node run to make sure your node runs on the expected network. For instance, to make sure that it runs on Ghostnet:

octez-node run --data-dir ~/tezos-ghostnet --network ghostnet

This command will fail with an error if the configured network is not Ghostnet. The node also displays the chain name (such as TEZOS_MAINNET) when it starts. Also mind opening the RPC interface as appropriate.

The list of built-in networks is in src/lib_node_config/ Octez developers edit the builtin_blockchain_networks_with_tags variable in this file to add or remove built-in networks.

Custom Networks

If the network you want to connect to is not in the list of built-in networks, you need a corresponding network configuration file. There are several ways to set that up. If you have an appropriate file, you can specify it with the --network argument when you initialize your node configuration (see above), and the node will load it. If you know a URL from which the file can be downloaded, you can also specify it with --network. The node will then download the config automatically. The network configuration should be in JSON format, containing an object matching the contents of the network field in config.json (see below for an example, and the node configuration documentation for reference).


The contents of the network configuration file will be saved in your node configuration file config.json, so it won’t be downloaded again on subsequent runs of the node.

Finally you can manually edit the main configuration file of the node (config.json). Here is an example configuration file for Mainnet:

  "p2p": {},
  "network": {
    "genesis": {
      "timestamp": "2018-06-30T16:07:32Z",
      "block": "BLockGenesisGenesisGenesisGenesisGenesisf79b5d1CoW2",
      "protocol": "Ps9mPmXaRzmzk35gbAYNCAw6UXdE2qoABTHbN2oEEc1qM7CwT9P"
    "chain_name": "TEZOS_MAINNET",
    "old_chain_name": "TEZOS_BETANET_2018-06-30T16:07:32Z",
    "incompatible_chain_name": "INCOMPATIBLE",
    "sandboxed_chain_name": "SANDBOXED_TEZOS_MAINNET",
    "user_activated_upgrades": [
        "level": 28082,
        "replacement_protocol": "PsYLVpVvgbLhAhoqAkMFUo6gudkJ9weNXhUYCiLDzcUpFpkk8Wt"
        "level": 204761,
        "replacement_protocol": "PsddFKi32cMJ2qPjf43Qv5GDWLDPZb3T3bF6fLKiF5HtvHNU7aP"
    "user_activated_protocol_overrides": [
        "replaced_protocol": "PsBABY5HQTSkA4297zNHfsZNKtxULfL18y95qb3m53QJiXGmrbU",
        "replacement_protocol": "PsBabyM1eUXZseaJdmXFApDSBqj8YBfwELoxZHHW77EMcAbbwAS"
        "replaced_protocol": "PtEdoTezd3RHSC31mpxxo1npxFjoWWcFgQtxapi51Z8TLu6v6Uq",
        "replacement_protocol": "PtEdo2ZkT9oKpimTah6x2embF25oss54njMuPzkJTEi5RqfdZFA"
        "replaced_protocol": "PtHangzHogokSuiMHemCuowEavgYTP8J5qQ9fQS793MHYFpCY3r",
        "replacement_protocol": "PtHangz2aRngywmSRGGvrcTyMbbdpWdpFKuS4uMWxg2RaH9i1qx"

This is equivalent to doing config init --network mainnet, or using "network": "Mainnet" in the configuration file (or to doing nothing, as Mainnet is the default), except that you will not automatically get updates to the list of bootstrap peers and user-activated upgrades (see Alias Versus Explicit Configuration).

  • genesis is the description of the genesis block, i.e. the first block of the chain. Inspect the genesis block using octez-client rpc get /chains/main/blocks/0 to find these values.

  • chain_name is the name of the network (nodes only talk to other nodes which use the same network name).

  • old_chain_name is usually the same as chain_name, except for networks that were renamed.

  • incompatible_chain_name is a name which must be different from chain_name and old_chain_name. It is thus ensured to be incompatible. It is used for testing purposes.

  • sandboxed_chain_name is the name of the network in sandbox mode. It can be the same as chain_name but it is safer to pick a different name.

  • user_activated_upgrades is the list of past user-activated upgrades. Each item has a field level, which is the level at which the protocol must be changed, and a field replacement_protocol, which is the hash of the protocol to switch to.

  • user_activated_protocol_overrides is the list of past user-activated protocol overrides. Each item has a field replaced_protocol and a field replacement_protocol. Both are protocol hashes. If replaced_protocol is to be activated using on-chain voting, replacement_protocol is activated instead.

  • default_bootstrap_peers is the list of addresses of default bootstrap peers. They are only used if p2p.bootstrap_peers is not present in the configuration file, and --no-bootstrap-peers is not given on the command-line.

Genesis Parameters

In addition to the above fields, you can also specify custom genesis parameters. That is, you can additionally specify the activation key:

  "p2p": {},
  "network": {
    "genesis": { ... },
    "genesis_parameters": {
      "context_key": "sandbox_parameter",
      "values": {
        "genesis_pubkey": "edpk..."

The genesis_parameters object contains:

  • context_key, the name of the key in the context part of the storage, whose value must be modified (if omitted, the default context key is sandbox_parameter);

  • values, which contains the protocol parameters.

In the above example, we set the genesis_pubkey parameter of proto_genesis.

Note that the genesis parameters that you specify in the configuration file can be overridden by the --sandbox parameter on the command-line. Similarly, if you are using a built-in network and if this built-in network comes with genesis parameters, you can override them with --sandbox.

Alias Versus Explicit Configuration

The previous sections explained two different ways to configure the network a node is connecting to:

  • alias configuration: using the name (also called the “alias”) of an existing, built-in network

  • explicit configuration: explicitly specifying the parameters of the network, which can be an existing or a custom network.

When connecting to existing networks, both options may apply, so here are some useful explanations to inform your choice.

If you use alias configuration, the configuration file stores the name of the network to connect to. For instance, if you configured it to connect to Ghostnet, it will contain something like:

  "p2p": {},
  "network": "ghostnet"

For Mainnet, it would contain mainnet, or nothing as this is actually the default.

When you update your node to new versions, built-in network parameters may change. For instance, the list of bootstrap peers may be updated with new addresses; new user-activated upgrades or user-activated protocol overrides may be added. Because the configuration file only contains the name of the network and not its parameters, it will automatically use the updated values.

However, if you use explicit configuration, the configuration file will no longer contain an alias such as mainnet or ghostnet. Instead, it will explicitly contain the list of bootstrap peers, user-activated upgrades and user-activated protocol overrides that you specify. This means that when you update your node, the updated values will not be used.

As a consequence, if you use explicit configuration, you need to update its parameters yourself when you update your node, unless you wish to keep the old network parameters.