genesis file

The genesis file is the file that allows you to create a new blockchain from block 0. It lays out the different parameter of your blockchain: the initial utxo, the start time, the slot duration time, etc...

Example of a BFT genesis file with an initial address UTxO and an account UTxO. More info regarding starting a BFT blockchain here and regarding addresses there. You could also find information regarding the jcli genesis tooling.

You can generate a documented pre-generated genesis file:

jcli genesis init

For example your genesis file may look like:

# The Blockchain Configuration defines the settings of the blockchain.

  # The block0-date defines the date the blockchain starts
  # expected value in seconds since UNIX_EPOCH
  # By default the value will be the current date and time. Or you can
  # add a specific time by entering the number of seconds since UNIX
  # Epoch
  block0_date: {default_block0_date}

  # This is the type of discrimination of the blockchain
  # of this blockchain is meant for production then
  # use 'production' instead.
  # otherwise leave as this
  discrimination: {discrimination}

  # The initial consensus version:
  # * BFT consensus: bft
  # * Genesis Praos consensus: genesis
  block0_consensus: bft

  # Number of slots in each epoch.
  # default value is {default_slots_per_epoch}
  slots_per_epoch: {default_slots_per_epoch}

  # The slot duration, in seconds, is the time between the creation
  # of 2 blocks
  # default value is {default_slot_duration}
  slot_duration: {default_slot_duration}

  # A list of Ed25519 PublicKey that represents the
  # BFT leaders encoded as bech32. The order in the list matters.
    - {leader_1}
    - {leader_2}

  # Genesis praos parameter D
  # default value: {default_bft_slots_ratio}
  bft_slots_ratio: {default_bft_slots_ratio}

  # Genesis praos active slot coefficient
  # Determines minimum stake required to try becoming slot leader, must be in range (0,1]
  # default value: {default_consensus_genesis_praos_active_slot_coeff}
  consensus_genesis_praos_active_slot_coeff: {default_consensus_genesis_praos_active_slot_coeff}

  # The fee calculations settings
  # total fees: constant + (num_inputs + num_outputs) * coefficient [+ certificate]
    # this is the minimum value to pay for every transaction
    constant: 2
    # the additional fee to pay for every inputs and outputs
    coefficient: 1
    # the additional fee to pay if the transaction embeds a certificate
    certificate: 4

  # The speed to update the KES Key in seconds
  # default value: {default_kes_update_speed}
  kes_update_speed: {default_kes_update_speed}

# Initial state of the ledger. Each item is applied in order of this list
  # Initial deposits present in the blockchain
  - fund:
      # UTxO addresses or account
      - address: {initial_funds_address}
        value: 10000

  # Initial certificates
  #- cert: ..

  # Initial deposits present in the blockchain
  #- legacy_fund:
  #    # Legacy Cardano address
  #    - address: 48mDfYyQn21iyEPzCfkATEHTwZBcZJqXhRJezmswfvc6Ne89u1axXsiazmgd7SwT8VbafbVnCvyXhBSMhSkPiCezMkqHC4dmxRahRC86SknFu6JF6hwSg8
  #      value: 123

There are multiple parts in the genesis file:

  • blockchain_configuration: this is a list of configuration parameters of the blockchain, some of which can be changed later via the update protocol;
  • initial: list of steps to create initial state of ledger

blockchain_configuration options

block0_datenumberthe official start time of the blockchain, in seconds since UNIX EPOCH
discriminationstringproduction or test
slot_durationnumberthe number of seconds between the creation of 2 blocks
epoch_stability_depthnumberallowed size of a fork (in number of block)
consensus_leader_idsarraythe list of the BFT leader at the beginning of the blockchain
max_number_of_transactions_per_blocknumberthe maximum number of transactions allowed in a block
bft_slots_rationumberplaceholder, do not use
linear_feesobjectlinear fee settings, set the fee for transaction and certificate publishing
consensus_genesis_praos_active_slot_coeffnumbergenesis praos active slot coefficient. Determines minimum stake required to try becoming slot leader, must be in range (0,1]
kes_update_speednumberthe speed to update the KES Key in seconds
slots_per_epochnumbernumber of slots in each epoch

for more information about the BFT leaders in the genesis file, see Starting a BFT Blockchain

initial options

Each entry can be one of 3 variants:

fundsequenceinitial deposits present in the blockchain (up to 255 outputs per entry)
certstringinitial certificate
legacy_fundsequencesame as fund, but with legacy Cardano address format


  - fund:
      - address: <address>
        value: 10000
      - address: <address2>
        value: 20000
      - address: <address3>
        value: 30000
  - cert: <certificate>
  - legacy_fund:
      - address: <legacy address>
        value: 123
  - fund:
      - address: <another address>
        value: 1001

fund and legacy_fund format

addressstringcan be a single address or an account address
valuenumberassigned value

legacy_fund differs only in address format, which is legacy Cardano